mercury handbook chemistry, applications and environmental impact · 2017-06-16 · mercury...
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Mercury HandbookChemistry, Applications and Environmental Impact
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Mercury HandbookChemistry, Applications and EnvironmentalImpact
Leonid F Kozin and Steve HansenEmail: [email protected], [email protected]
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Technical Editor: Cezary GuminskiTranslated by Mark Kit
ISBN: 978-1-84973-409-7
A catalogue record for this book is available from the British Library
r L F Kozin and S C Hansen 2013
All rights reserved
Apart from fair dealing for the purposes of research for non-commercial purposes or forprivate study, criticism or review, as permitted under the Copyright, Designs and PatentsAct 1988 and the Copyright and Related Rights Regulations 2003, this publication may notbe reproduced, stored or transmitted, in any form or by any means, without the priorpermission in writing of The Royal Society of Chemistry or the copyright owner, or in thecase of reproduction in accordance with the terms of licences issued by the CopyrightLicensing Agency in the UK, or in accordance with the terms of the licences issued by theappropriate Reproduction Rights Organization outside the UK. Enquiries concerningreproduction outside the terms stated here should be sent to The Royal Society ofChemistry at the address printed on this page.
The RSC is not responsible for individual opinions expressed in this work.
Published by The Royal Society of Chemistry,Thomas Graham House, Science Park, Milton Road,Cambridge CB4 0WF, UK
Registered Charity Number 207890
Visit our website at www.rsc.org/books
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Preface
The Mercury Handbook attempts to cover all of the basic subject matterrelated to the condensed phase physics, chemistry, metallurgy, applicationand environmental aspects of mercury. The present book is derived fromLeonid F. Kozin’s book on the physical chemistry and metallurgy of high-purity mercury (Fizikokhimiia i Metallurgiia Vysokochistoi Rtuti i ee Splavov).The original Russian text was translated by Mark Kit of Language Interface inNew York. Unfortunately a large percentage of the original work remains inRussian at the present time. Dr. Cezary Guminski assisted in the translationand technical editing of the book and also wrote a chapter on the use ofmercury in small-scale gold mining.
Numerous important contributions were made to the book by others. JasonGray of Nippon Instruments North America explained the practicaloperation of atomic fluorescence spectroscopy. A thorough discussion of themedical symptoms of mercury intoxication was generously providead byBethlehem Apparatus, Inc. of Hellertown, Pennsylvania. The University ofIllinois at Urbana-Champaign has provided invaluable access to its vastcollection of online and print journals. Dr. Tim Brumleve of APL EngineeredMaterials, Inc. has assisted in the proof reading of key chapters of thepresent book.
The authors wish to thank their families for their extraordinary patienceduring the writing and editing of the manuscript. The staff of the Royal Societyof Chemistry has endured more than necessary and is complimented for theirprofessionalism and for their patience. Special mention should be given toMrs. Janet Freshwater, Mrs. Alice Toby-Brant, Ms. Sarah Salter, Mrs. KatrinaHarding, Mrs Rosalind Searle and others. They were exceptionally polite andpatient throughout the entire writing process. Lastly, the staff of Strawberry
Mercury Handbook: Chemistry, Applications and Environmental Impact
By Leonid F Kozin and Steve Hansen
r L F Kozin and S C Hansen 2013
Published by the Royal Society of Chemistry, www.rsc.org
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Fields in Urbana has provided encouragement and refreshment throughout thearduous task of writing this monograph. Additional information and updatesto the Mercury Handbook can be found at www.mercuryhandbook.com.
Leonid F. KozinKyiv, Ukraine
Steve C. HansenUrbana, Illinois
vi Preface
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Contents
Chapter 1 Physicochemical Properties of Metallic Mercury 1
1.1 Atomic Properties 11.2 Crystallography 3
1.2.1 P–T Diagram 31.3 Melting Point 41.4 Heat of Fusion 41.5 Heat Capacity 41.6 Thermal Conductivity 61.7 Emissivity 91.8 Boiling Point, Heat and Entropy of
Vaporization 9
1.9 Vapor Pressure 101.9.1 Solid Mercury 101.9.2 Liquid Mercury 121.9.3 Triple Point 121.9.4 Critical Temperature and Pressure 13
1.10 Density 141.11 Surface Tension 171.12 Viscosity 181.13 Isothermal Compressibility 191.14 Thermal Expansion Coefficient 201.15 Self-diffusion 211.16 Electrical and Magnetic Properties 241.17 Hall Coefficient 261.18 Superconductivity 271.19 Excited-state Properties 27References 28
Mercury Handbook: Chemistry, Applications and Environmental Impact
By Leonid F Kozin and Steve Hansen
r L F Kozin and S C Hansen 2013
Published by the Royal Society of Chemistry, www.rsc.org
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Chapter 2 Amalgam Solubility 36
2.1 Solubility of Metals in Mercury 362.2 Amalgams with Compounds Formed in the
Solid Phase 40
References 46
Chapter 3 Diffusion of Metals in Mercury 50
3.1 Effect of Atomic Size on Diffusion 503.1.1 Effect of Atomic Radius 51
3.2 Temperature Dependence of Diffusion in Amalgams 543.3 Concentration Effects on Diffusion 553.4 Diffusion of Mercury in Solid Metals 57References 58
Chapter 4 Purification of Mercury Using Chemical and Electrochemical
Methods 61
4.1 Technical Requirements for Mercury 614.2 Chemical Methods for Mercury Treatment 624.3 Single-stage Electrochemical Methods for Obtaining
High-purity Mercury 75
References 77
Chapter 5 Chemical Properties of Mercury 80
5.1 Inorganic Mercury Compounds 805.1.1 Disproportionation in Hg2þ2 and Hg21 805.1.2 Solubility of Metallic Mercury in Water 815.1.3 Solubility of Mercury in Ionic Solutions 84
5.2 Mercury(I) and Mercury(II) Halides and
Pseudohalides 86
5.2.1 Mercury(I) Fluoride – Hg2F2 875.2.2 Mercury(II) Fluoride – HgF2 875.2.3 Mercury(I) Chloride (Calomel) – Hg2Cl2 895.2.4 Mercury(II) Chloride (Corrosive Sublimate) –
HgCl2 905.2.5 Mercury(I) Bromide – Hg2Br2 965.2.6 Mercury(II) Bromide – HgBr2 975.2.7 Mercury(I) Iodide – Hg2I2 1015.2.8 Mercury(II) Iodide – HgI2 1035.2.9 Mixed Mercury(II) Halides 106
viii Contents
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5.2.10 Mercury(II) Cyanide – Hg(CN)2 1065.2.11 Mercury(I) Dithiocyanate – Hg2(SCN)2 1085.2.12 Mercury(II) Dithiocyanate – Hg(SCN)2 108
5.3 Oxygen Compounds of Mercury(I) and Mercury(II) 1095.3.1 Mercury(I) Oxide – Hg2O 1095.3.2 Mercury(II) Oxide – HgO 1105.3.3 Mercury(I) Nitrate Dihydrate –
Hg2(NO3)2 � 2H2O 1145.3.4 Mercury(II) Nitrate – Hg(NO3)2 1155.3.5 Mercury(I) Perchlorate – Hg2(ClO4)2 1165.3.6 Mercury(II) perchlorate – Hg(ClO4)2 116
5.4 Organometallic Mercury Compounds 1165.4.1 Organometallic Mercury(I) Compounds 1165.4.2 Organometallic Mercury(II) Compounds 117
References 120
Chapter 6 Electrochemical Properties of Mercury 128
6.1 Kinetics and Mechanism of Discharge and Ionization
of Mercury in Simple Electrolytes 128
6.2 Kinetics and Mechanism of Discharge and Ionization
of Mercury in Complex-forming Media 138
References 140
Chapter 7 Lighting 143
7.1 Introduction 1437.1.1 Lamp Color and Quality Measurements 144
7.2 Fluorescent Lighting 1447.2.1 Mercury Content in Fluorescent Lamps 1467.2.2 Amalgam-controlled Mercury Vapor
Pressure 1467.2.3 Temperature-controlled Amalgams 1477.2.4 Mercury Dispensers 149
7.3 Measurement of Mercury Vapor Pressure of
Fluorescent Lamp Amalgams 151
7.3.1 Vapor Pressure Measurement System 1517.3.2 Atomic Absorption Spectrometry 1527.3.3 Knudsen Effusion Mass Spectrometry 152
7.4 High-pressure Mercury Lamp 1527.5 Ultra-high-performance Lamps 1537.6 High-pressure Sodium Lamps 1547.7 Metal Halide Lamps 157References 159
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Chapter 8 Synthesis of Semiconducting Compounds 163
8.1 Synthesis of Semiconducting Mercury Compounds 1638.1.1 Sublimation and Resublimation Methods 1708.1.2 Methods Used to Grow Single Crystals 170
8.2 Indirect Synthesis of Mercury Chalcogenides 1718.2.1 Transport Reactions Method 1728.2.2 Epitaxial Layer Growth 174
References 176
Chapter 9 Chlor-Alkali Process 180
9.1 Introduction 1809.2 Electrochemistry of the Mercury Cathode Process 1809.3 Sodium–Mercury Phase Diagram 1819.4 Production of Chlorine 185References 191
Chapter 10 Use of Mercury in Small-scale Gold Mining 193
Cezary Guminski
10.1 Introduction 19310.1.1 Reasons for Artisanal Gold Mining 19410.1.2 Mercury Pollution 194
10.2 Method of Artisanal Gold Mining 19410.3 Environmental Degradation Caused by Small-scale
Gold Mining 196
10.4 Remedies or Improvements to Small-scale
Gold Mining 197
References 198General References 198
Chapter 11 Mercury Legislation in the United States 199
11.1 Introduction 19911.2 Mercury Legislation 199
11.2.1 Mercury Export Ban Act 20011.2.2 Mercury-containing and Rechargeable
Battery Management Act 20111.2.3 Legislation Controlling Mercury Release 20111.2.4 Food and Drug Administration 204
11.3 Mercury Regulations and Standards 20411.3.1 Measurement of Mercury in Water 20511.3.2 Land Disposal Restrictions 20511.3.3 Mercury in Air 205
11.4 Occupational Safety and Health Administration 207
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11.5 Department of Transportation and International
Air Transport Association 207
References 208
Chapter 12 Environmental Aspects of the Industrial Application of
Mercury 209
Leonid F. Kozin, Steve C. Hansen, Nikolai F. Zakharchenko
and Jason Gray
12.1 History and Uses of Mercury 20912.2 Occurrence of Mercury in Nature 21012.3 Recovery of Mercury from HgS 21112.4 Amounts of Mercury Used in Industry 21212.5 The Role of Industry in Environmental
Mercury Pollution 214
12.6 Mercury Pollution 21612.7 Environmental Mercury 21712.8 Mercury Detection by Atomic Fluorescence
Spectrometry 219
12.8.1 Atomic Fluorescence Spectrometry 21912.8.2 Application of CVAFS for the
Determination of Mercury in Water 220References 222
Chapter 13 Demercurization Processes in Different Sectors of Industry 228
Leonid F. Kozin, Steve C. Hansen and Nikolai F. Zakharchenko
13.1 Introduction 22813.2 Demercurization of a Chlor-Alkali Plant 22813.3 Recycling of Fluorescent Lamps 230
13.3.1 Thermal Demercurization of FluorescentLamps 230
13.3.2 Vibration–Pneumatic DemercurizationMethod 232
13.3.3 Hydrometallurgical Treatment forFluorescent Lamp Recycling 233
13.4 Removal of Mercury from Industrial Wastewater 23413.5 Demercurization of Workplaces and Plants 235References 237
Chapter 14 Safety and Health Practices for Working with Metallic
Mercury 241
Woodhall Stopford
14.1 Toxicity of Metallic Mercury 24114.2 Toxicity from Chronic Exposure 242
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14.3 Surveillance Programs for Industry 24314.4 Preventive Measures 245Further Reading 247
Appendix I Phase Diagrams and Intermetallic Compounds in Binary
Amalgam Systems 248
AI.1 Binary Mercury Phase Diagrams 248AI.2 Intermetallic Phases in Binary Amalgam Systems 248
Appendix II Density and Surface Tension of Binary Amalgams 272
Appendix III Inorganic and Organic Mercury Compounds 282
Appendix IV Selected Organometallic Compounds of Mercury 297
Appendix V Solubility of Common Metals in Mercury 300
Subject Index 312
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CHAPTER 1
Physicochemical Properties ofMetallic Mercury
1.1 Atomic Properties
High-purity mercury is a dense, silvery white liquid with an extraordinarilylow melting point of 234.321K or –38.829 1C.1 Mercury is a metal fromSubgroup IIB of the Periodic Table and is related to zinc and cadmium.Mercury has the atomic number 80, atomic mass 200.59 and atomic volume14.26�10–6m3mol–1 at 298K.2 Its electronic configuration
ls22s22p63s23p63d104s24p64f144d105s25p65d106s2
(or more simply, Xe shell 4f145d106s2) qualifies it as a non-transition metal.It has valence states of þ1 and þ2. Natural mercury consists of sevenstable isotopes3 and 17 synthetic and radioactive isotopes with mass numbers185–206. The natural mercury isotopes have the following mass numbers andabundances:
Isotope Abundance (%)196 0.146198 10.02199 16.84200 23.13201 13.22202 29.80204 6.85
The isotope with mass number 194 (194Hg) has a half-life of 130 days, 203Hg47 days and 199Hg 2.4�10–9 s. Isotopes of mercury can be obtained through thefollowing reactions:
19680Hgþ 1n! 197
80Hgþ g ð1:1Þ
Mercury Handbook: Chemistry, Applications and Environmental Impact
By Leonid F Kozin and Steve Hansen
r L F Kozin and S C Hansen 2013
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20480Hgþ 2
1H2 ! 20580Hgþ 1
1H ð1:2Þ
19779HgþH! 195
80Hgþ 3n ð1:3Þ
19879Auþ 1p! 199
80Hgþ g ð1:4Þ
The thermal neutron capture cross-section for natural mercury is 380� 20barn. Atomic and ionic ionization potentials (j) and their radii are asfollows:
Hg0-Hg1 Hg1-Hg21 Hg21-Hg 31
j (eV) 10.438 18.756 34.2Orbital radius (nm) 0.1126 (Hg) 0.1099 (Hg1) 0.0605 (Hg21)
The energy required for electron shell transfer from the basic state 6s2
(i.e. transfers 6s2-6s1p1) is fairly large (524.26 kJmol–1) 4 and demonstratesthe chemical inertness of metallic mercury. Moreover, the high 6s-6p transferenergy gives evidence that mercury tends to form two covalent bonds (and, as aresult, further bonding of ligands is difficult). In contrast with the high energyof s,p transfer, 5d10-5d9s1 and 5d10-5d9p1 transfers in Hg21 ions require avery low energy of 5.3 and 14.7 eV, respectively.4 The electron affinity fora-mercury (a-Hg) is 1.54 eV, for b-Hg it is 1.37 eV and the electron workfunction is 4.52 eV.5 The electronegativity of mercury, according to differentauthors, is given in Table 1.1.
The atomic, covalent and ionic radii of mercury5 are given in Table 1.2.
Table 1.1 Electronegativity values of mercury.
Electronegativity (eV) Ref.
1.9 62.0 7, 81.9 91.92 101.8 11
Table 1.2 Atomic radii of mercury.
Radius Distance (nm) Coordination No.
Atomic radius 0.155Covalent radius 0.149Ionic radius of Hg21 0.112Physical radius of Hg1 0.111 3
0.133 6Physical radius of Hg21 0.083 2
0.110 40.116 60.128 8
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1.2 Crystallography
Solid mercury has a rhombohedral structure (a-Hg) with the lattice parametersa¼ 0.29925 nm (2.9925 A), b¼ 701 440 600. Each atom of mercury is surroundedby six neighboring atoms at a distance of 0.300 nm and six other atoms at adistance of 0.347 nm.
1.2.1 P–T Diagram
The P–T diagram for mercury12 is given in Figure 1.1.a-Hg: Mercury is a liquid under ambient conditions but crystallizes into the
a-Hg structure at room temperature upon compression to 1.2GPa.13
b-Hg: The a-Hg structure transforms to the b-Hg structure at 3.4GPa atroom temperature.13 The b-Hg lattice, formed at temperatures below 79K, is abody-centered tetragonal structure with lattice parameters a¼ 0.3995nm,c¼ 0.2825nm.14 The space group of b-Hg is I4/mmm.13 Swenson15,16 determinedthe enthalpy of the solid-state transition a-Hg-b-Hg to be DHa-b¼ 122 Jmol–1, the volume change to be DVa-b¼ –0.21 cm3mol–1 and the entropy oftransformation to be DSa-b¼ –1.54 JK–1mol–1 at –194 1C and 0.101MPa.
g-Hg: According to Takemura et al.,17 the structure of g-Hg is monoclinic,C2/m. It forms at 12GPa,12 with six atoms in the unit cell. Each mercury atomis coordinated by 10–11 atoms.
d-Hg: The structure of hexagonal close-packed (hcp) d-Hg forms at pressuresabove 37GPa18 and is reported to be stable up to 193GPa. At 193GPa, thelattice parameters are a¼ 0.2612 nm and c¼ 0.4284 nm, which give c/a¼ 1.640.The c/a ratio of mercury under high pressure decreases from 1.75 at 50GPa to1.64 at about 200GPa.12,18 Yan et al.19 also reported results on the high-pressure behavior of mercury.
Abell and King20 performed mechanical tests on solid mercury below 77K.Solid mercury turns white and becomes ductile at low temperatures and was
Figure 1.1 P–T phase diagram of mercury according to Schulte and Holzapfel.12 Closedand open symbols represent forward and backward transitions, respectively.Reprinted with permission from O. Schulte and W. B. Holzapfel, Phys. Rev.B, 1993, 48, 14009 [http://jpsj.ipap.jp/link?JPSJ/76/023601/]. Copyright (c)1993 by the American Physical Society. Ref. 12.
Physicochemical Properties of Metallic Mercury 3
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found to recrystallize at B160K. Slip in single crystals of mercury was studiedby Rider and Heckscher.21 At 90K, solid mercury deforms by slip andtwinning. Plastic deformation of Hg single crystals has also been studied.22,23
At the melting temperature, the structure of liquid mercury is close to that ofsolid mercury. Each atom is surrounded by six other atoms at a distance of0.307 nm. Thus, at the melting temperature, the coordination number in theliquid is 6, the same as for solid mercury. With increase in temperature, themercury coordination number increases as follows:24
T (K) Coordination No.234.9 6.0296 8.2–8.3301 10–11
1.3 Melting Point
Mercury is the lowest melting point metal. Its melting point, measured bydifferent groups, is given in Table 1.3. The data indicate the high purity of thesamples studied. With increase in pressure, the melting point of mercury shiftstowards higher temperature, dT/dP¼ 42.44–49.84KGPa–1. Between 1.01325 and6.0795GPa, the melting point of mercury increases from 286.9� 0.3 to 515K.31,33
1.4 Heat of Fusion
The heat of fusion (DHfusion) of mercury, according to different sources, is givenin Table 1.3. The heat of fusion increases with increase in pressure. At apressure of 1.01325 MPa the heat of fusion is 2623� 83.7 Jmol–1 and at2.0265GPa it is 2958� 83.7 Jmol–1.33
1.5 Heat Capacity
The heat capacity of mercury has been studied over a broad range oftemperatures.30,36,37 The dependence of the specific heat capacity of mercury on
Table 1.3 Melting point and heat of fusion of mercuryat 1 atm (101.325 kPa).
T (K) T (1C) DHfusion (Jmol–1) Ref.
234.45 –38.700 2320 25234.31 –38.840 2295 26234.40 –38.750 2301 27
2301.2� 20.9 282310� 10 292295� 40 302343 312308 32
234.288 –38.862� 0.003 33234.314 –38.836 34234.34 –38.810 27234.33� 0.01 –38.82 35
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temperature is shown in Figure 1.2. The heat capacity of solid mercury wasdetermined by Regel and Glazov36 with 257 experimental points and by Buseyand Giaque.26 In the temperature range 150.90–233.79K, the heat capacitycurve is represented by two temperature ranges:36
171:03oTo215:54K
213:20oTo233:58K
In the first range, the molar heat capacity of solid mercury is described by theequation36
Cp ¼ Cvibr þ Cel þ Can þ Cvac ð1:5Þ
where Cvibr is the lattice vibration contribution, Cel is the electroniccontribution, Can is the anharmonic contribution and Cvac is the vacancycontribution. The sum of the lattice vibration contribution is calculated usingthe equation
Cvibr ¼ 3R 1� 0:05 YD=Tð Þ2h i
ð1:6Þ
where YD is the Debye temperature, which for a-Hg is 79K.38 Cel is the molarelectronic contribution:
Cel ¼ gT ð1:7Þ
where g is a constant equal to 1.81mJmol–1K–2.39 Can is the anharmoniccomponent of Cp:
Cel þ Can ¼ BT þDT2 ð1:8Þ
T, K0 1 2 3 4 5
Cp,
mJ
- mol
–1 K
–1
0
200
400
600
800
1000
1200
Figure 1.2 Low temperature heat capacity of mercury.40
Physicochemical Properties of Metallic Mercury 5
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where B and D are constants. Cvac is the vacancy contribution:
Cvac ¼ ðLU20=RT
2Þexpð�U0=RTÞ ð1:9Þ
where U0 is the vacancy formation energy. The constants B, D and L in eqns(1.8) and (1.9) are found through the least-squares analysis of the U0–T rela-tionship in a given range of values. Experimentally obtained values of molarheat capacity of solid and liquid mercury are given in Tables 1.4 and 1.5.Constant-pressure heat capacity values at very low temperatures, below 20K,were measured by van der Hoeven and Keesom40 and others.41–43 Van derHoeven and Keesom measured an electronic specific heat coefficient of1.79� 0.02mJmol–1K–2.
Analysis of the data in Table 1.5 reveals that in the temperature range140–234K, when approaching the melting temperature, the heat capacity ofmercury increases non-linearly with increase in temperature.30 The heatcapacity of mercury at high temperatures [Figure 1.3] does not differ muchfrom the classical value (Cp/3R¼ 1.13), which is due to the small effect of theanharmonic and electronic contributions.44
1.6 Thermal Conductivity
The thermal conductivity of solid mercury is anisotropic. The thermalconductivity of mercury single crystals on the trigonal axis (l8) and perpen-dicular to it (l?), in the temperature range 80–234.288 K, is described by eqns(1.10) and (1.11), respectively.45
ljj ¼ ð44:8� 0:0237TÞWm�1K�1 ð1:10Þ
l? ¼ ð31:4� 0:0279TÞWm�1K�1 ð1:11Þ
Table 1.4 Specific heat of mercury at temperatures below 20K. Data fromRef. 40.
T (K) Cp (mJmol–1 K–1) T (K) Cp (mJmol–1 K–1)
0.3522 0.233 1.178 11.330.3669 0.263 1.286 16.620.3968 0.336 1.451 27.330.4243 0.406 1.665 47.930.4529 0.488 1.822 68.710.4809 0.587 2.000 98.150.5173 0.729 2.241 150.30.5766 1.001 2.485 216.00.6328 1.323 2.842 335.60.7189 1.968 3.230 495.60.7790 2.535 3.499 626.80.8480 3.383 3.746 754.80.9228 4.542 3.956 874.70.9947 5.943 4.121 965.6
4.273 1036.7
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Table 1.5 Experimental values of molar heat capacity of solid and liquidmercury. Data from Ref. 30.
T (K)
Cp
(J mol –1
K–1) T (K)
Cp
(J mol –1
K–1) T (K)
Cp
(J mol–1
K–1) T (K)
Cp
(J mol –1
K–1)
5.19 1.834 29.97 14.78 89.66 23.74 193.50 27.095.62 2.068 31.46 15.30 92.44 23.88 203.46 27.406.12 2.361 32.90 15.81 95.17 24.02 209.10 27.586.72 2.658 34.32 16.27 97.86 24.14 214.70 27.777.36 2.994 35.82 16.71 100.71 24.27 217.44 27.877.97 3.304 37.34 17.18 103.72 24.40 219.60 27.958.64 3.669 38.88 17.58 106.69 24.51 222.18 28.059.33 4.076 40.44 17.98 109.62 24.62 224.75 28.149.97 4.439 42.09 18.37 113.03 24.75 227.30 28.2410.80 4.946 43.89 18.77 117.09 24.89 229.84 28.3411.89 5.650 46.94 19.39 121.76 25.04 232.37 28.4512.93 6.351 49.11 19.79 126.88 25.21 237.90 28.5013.87 6.998 51.22 20.15 130.94 25.37 239.14 28.4914.77 7.542 56.58 20.97 136.00 25.48 240.63 28.4815.66 8.097 58.98 21.29 140.99 25.62 242.64 28.4316.80 8.646 61.32 21.57 145.92 25.76 245.98 28.4117.76 9.183 63.97 21.85 150.78 25.90 250.56 28.3518.77 9.719 66.93 22.15 155.60 26.03 256.35 28.2919.86 10.28 69.90 22.41 160.12 26.16 263.46 28.2220.98 10.85 72.89 22.66 164.60 26.28 271.09 28.1522.11 11.41 75.81 22.89 169.28 26.41 278.15 28.1023.27 11.97 78.67 23.08 174.10 26.55 285.19 28.0224.66 12.61 82.25 23.61 179.02 26.68 292.20 27.9826.17 13.27 84.25 23.43 183.88 26.81 297.19 27.9327.74 13.90 86.94 23.59 188.71 26.95 299.05 27.89
Figure 1.3 Specific heat capacity of mercury versus temperature.26,30
Physicochemical Properties of Metallic Mercury 7
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The thermal conductivity of liquid mercury, shown in Figure 1.4, has beenextensively studied. The main contribution to the thermal conductivity of liquidmercury is made by conduction electrons. Therefore, the main heat flux inmetallic mercury is transmitted, as in other metals, by conduction electrons.
The ratio of thermal conductivity, l, to electrical conductivity, s, at a giventemperature is called the Lorentz number, L:
L ¼ lsT
ð1:12Þ
Lorentz numbers calculated for the main axes of mercury single crystals agreewithin 3%.45 Table 1.6 gives the values of the Lorentz number at differenttemperatures.
Figure 1.4 Thermal conductivity of liquid mercury as a function of temperature withprevious results reported by various investigators Refs. 46, 50, 51. Thermalconductivity of liquid mercury as a function of temperature is alsoreported by Refs. 47–49, 52–55 and calculated by Ref. 55.Adapted with kind permission from Refs. 46, 50, 51.
Table 1.6 Lorentz number of mercury (WOK–2).
T (K) T (1C) L�10–8 (WOK–2) Ref.
303 30 2.75 56348 75 2.50 57373 100 2.47 57423 150 2.45 57473 200 2.45 57
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1.7 Emissivity
The emission coefficient, el, of mercury from a smooth non-oxidized surface is0.10–0.12. However, the reflectivity of polished solid mercury and a liquidsurface, w, for light flux of wavelength l is as follows:2
Form Wavelength, l (mm) Reflectivity, w (%)Solid 0.45–0.70 72.3–72.8Liquid 0.75–1.00 77.3–77.9
1.8 Boiling Point, Heat and Entropy of
Vaporization
The boiling point of mercury (Tboil) has been reported in the literature withan accuracy of 0.01–0.08 1C. Experimental results along with the heat ofvaporization are given in Table 1.7.
According to Hultgren et al.,68 mercury vapor is best described as a non-idealmonomer.
Values for the heat of evaporation (DHevap) and entropy ofvaporization (DSevap) also depend on pressure. Table 1.8 summarizes DHevap
and DSevap values33 at different pressures. Thermodynamic values for
Table 1.7 Boiling point and heat of vaporization of mercury.
Tboil (K) Tboil (1C)Heat of vaporization,DHvap (kJ mol–1) Ref.
629.814 356.664 58629.7653 356.6153 59629.7683 356.6183 60
59.10 2661.42 6161.41 6261.40 6361.44 6461.02 6561.29 6661.76 67
Table 1.8 Enthalpy and entropy of evaporation of mercury.33
P (Pa) DHevap (kJ mol–1) DSevap (J mol–1 K–1)
3.07 �10–4 61.883� 0.0628 264.1362.62 �10–1 61.404� 0.0628 205.9361.013 �10–5 59.228� 0.0628 94.0563
Physicochemical Properties of Metallic Mercury 9
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the sublimation of mercury at 234.288K are DHsubl¼ 64.1784� 0.06276 kJmol–1 and DSsubl¼ 273.926 Jmol–1K–1.33
1.9 Vapor Pressure
Studies of the temperature dependence of mercury vapor pressure weresummarized by Huber et al.69,70 Diatomic molecules of Hg2 were found inmercury vapor.71 Hg2 molecules oscillate at B36 cm–1, their internucleardistance is 3.34�10–10 m and their dissociation energy is 7.53� 2.09 kJ mol–1.72
Values of the heat of sublimation of monatomic and diatomic molecules are61.304� 0.063 and 103.64 kJmol–1, respectively. The heat of dimerization ofmercury is 8.008 kJmol–1.73 A small energy of dissociation of Hg2 molecules inthe vapor causes gaseous mercury to be virtually monatomic and to havesignificant vapor pressure even at low temperatures. The thermodynamicproperties of Hg2 molecules were also studied by Hilpert.74
1.9.1 Solid Mercury
Measurements of the vapor pressure over solid mercury are relatively scarce.Values obtained by Poindexter67 are given in Table 1.9.
The vapor pressure over solid mercury75 is given by
logP ðPaÞ ¼ 5:00572
þ 9:453� 0:2011� logT � 6:558� 10�4T � 3379
T
� �ð1:13Þ
The saturated vapor pressures over a broad range of temperatures for solid andliquid mercury are fairly consistent. Analysis of experimental data in coor-dinates of lnPHg–1/T
70 demonstrated good agreement between data fromdifferent authors. The most accurate results are shown in Figure 1.5. ThelnPHg–T curve in Figure 1.5 also shows the triple point, boiling point andcritical temperature.70
Table 1.9 Vapor pressure above solid mercury.67
T (K) T (1C) P (kPa)
193.58 –79.57 4.00�10–10203.25 –69.90 8.00�10–10206.30 –66.85 5.33�10–9209.47 –63.68 1.69�10–9215.43 –57.72 6.47�10–9216.31 –56.84 6.91�10–9223.30 –49.85 3.16�10–8229.75 –43.40 9.75�10–8230.38 –42.77 1.00�10–7231.39 –41.76 1.14�10–7
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Figure 1.5 Mercury vapor pressure versus temperature. For the references that appear in the key, please refer to the original reference.70
Official contribution of the National Institute of Standards and Technology; not subject to copyright in the United States.
Physico
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1.9.2 Liquid Mercury
Based on a great amount of data, Nesmeyanov76 suggested the followingrelationship between vapor pressure and temperature for liquid mercury up to673K (400 1C):
logP ðPaÞ ¼ 5:00572
þ 216:70428� 9078:658
Tþ 0:05481736T � 82:87205� logT
� �
ð1:14Þ
The vapor pressure of mercury according to the literature26,77 in thetemperature range 298–629.810K (Tboil) can be determined using the equation
logP ðPaÞ ¼ 5:00572þ 10:355� 0:795� logT � 3305
T
� �ð1:15Þ
A more elaborate vapor pressure equation for mercury was suggested byHuber et al.69,70 Very accurate experimental measurements of the vapor pressureof mercury were performed by Beattie et al.59 from 623 to 636K and by Speddingand Dye78 from 534 to 630K. The normal boiling point of mercury wasdetermined by Beattie et al. as 629.7653� 0.0016K on the ITS-90 internationaltemperature scale.79 Table 1.10 gives the vapor pressure of mercury up to itsnormal boiling point and Table 1.11 above the normal boiling point.
At very high temperatures, a small but noticeable change in slope on thevapor pressure curve occurs. A metal–non-metal transition80 occurs atB1360K (1087 1C).
1.9.3 Triple Point
When analyzing the thermodynamic parameters of mercury, it was foundthat the triple point is located at 234.3156K with a vapor pressure of
Table 1.10 Vapor pressure of saturated mercury up to the boiling point.78
T (K) T (1C) P (kPa)
533.825 260.675 13.06549.811 276.661 19.337558.948 285.798 23.954564.721 291.571 27.351565.743 292.593 27.964573.610 300.460 33.293586.013 312.863 43.390594.741 321.591 51.918597.253 324.103 54.588604.288 331.138 62.792613.886 340.736 75.568620.254 347.104 85.144630.244 357.094 102.22
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PHg¼ 0.157 Pa (1.55�10–6 Torr).1 This value is close to the values calculatedby means of eqns (1.18) and (1.19), namely 3.33�10–4 and 3.35�10–4 Pa(2.510�10–6 and 2.514�10–6 Torr), respectively. Table 1.12 gives experi-mentally determined values of the triple point of mercury.
1.9.4 Critical Temperature and Pressure
Table 1.13 gives measurements of the critical temperature and pressure ofmercury.70 The coexistence curve of liquid and gaseous mercury is shown inFigure 1.6.
Table 1.12 Triple point of mercury.
T (K) T (1C) Temperature scale Ref.
234.3156 –38.8344 ITS-90 81234.3159 –38.834 ITS-90 82234.316 –38.834 29234.314 –38.836 IPTS-68 34234.3083 –38.842 IPTS-68 83234.3086 –38.841 IPTS-68 84234.306 –38.844 85
Table 1.11 Vapor pressure of mercury above the boiling point.58
T (K) T (1C) P (kPa) P (mmHg)
629.814 356.664 101.325 760670.06 396.91 200 1500733.41 460.26 500 3750790.2 517.05 1000 7500856.7 583.55 2000 15 000964.8 691.65 5000 375�1041068 794.85 10 000 7.5�1041197 923.85 20 000 1.5�1051425 1151.85 50 000 3.75�1051639 1365.85 100 000 7.5�1051765 1491.85 151 000 1.13�1061769� 0.042 1495.85 153 000 1.15�106
Table 1.13 Critical temperature and pressure of mercury. Adapted fromRef. 70.
Tc (K) Tc (1C) Pc (MPa) rc (g cm–3) Ref.
1750 1477 172 861751� 1 1478� 1 167.3 5.8 871751� 1 1478� 1 167.3� 0.2 5.77 881753 1480 152� 1 891763.15� 15 1490� 15 151� 3 4.2� 0.4 90, 911764� 1 1491� 1 167� 3 921768� 8 1495 167.5� 2.5 93
Physicochemical Properties of Metallic Mercury 13
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1.10 Density
The density of mercury has been extensively studied. Literature values of thedensity of solid and liquid mercury are listed in Table 1.14 and plotted inFigure 1.7.
Solid mercury at 234.25K has a density of 14.193 g cm–3,96 and liquidmercury at 234.288K has a density of 13.691 g cm–3. The change in density atthe liquid–solid transition is þ3.5–3.7% (compared with the density of solidmercury). The volume change upon solidification is given in Table 1.15.Further studies on the density of mercury have been reported.105–113
Analysis of the density of liquid mercury as a function of temperaturehas shown that it may be expressed by a linear equation. Equation (1.16)gives the density of solid mercury versus temperature in the range 50–234.288K:
d ¼ d0 þ T0 � Tð Þ drdT
� �ð1:16Þ
where T0 is the melting temperature of mercury, d0 is the density of liquidmercury at the melting point T0, equal to 13.690 g cm–3, and dr/dT is thetemperature coefficient, –2.4386� 0.01744 g cm–3K–1.
Experimental and calculated (straight line) values for the density of solid andliquid mercury are presented in Figure 1.7, showing good agreement of the
Two phase region
Figure 1.6 Phase diagram of liquid and gaseous mercury. The dashed line indicatesthe liquid–vapor coexistence curve. With kind permission from Taylor &Francis Ltd. D. R. Postill, R. G. Ross and N. E. Cusack, ‘Equation ofstate and electrical resistivity of liquid mercury at elevated temperaturesand pressures’, Adv. Phys., 1967, 16, 493.95
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data. According to Duval,115 the equation for calculating the density ofmercury at a selected temperature (t, 1C) is more complex:
d ¼ 13:595080
1þ1:814401�10�4tþ7:016�10�9t2þ2:8625�10�11t3þ2:617�10�14t4g cm�3
ð1:17ÞValues for the density of liquid and gaseous mercury along the saturation line
have been determined,95,100,116 and Table 1.16 reports values for the density ofgaseous mercury from 968 to 1523K.117
Table 1.14 Density of solid and liquid mercury.
T (K) T (1C) r (g cm–3) Ref.
77 –196.15 14.70 1578.15 –195 14.49 9782.15 –191 14.469 98194.15 –79 14.29 97234.321 –38.829 14.182 31234.321 –38.829 13.690 99293.15 20 13.5460 95,100293.15 20 13.545892 101293.15 20 13.545884 102298.15 25 13.5338 95,100303.15 30 13.5213 103313.15 40 13.4969 103323.15 50 13.4725 103333.15 60 13.4482 103343.15 70 13.4239 103353.15 80 13.3997 103363.15 90 13.3755 103373.15 100 13.3514 103383.15 110 13.3273 103393.15 120 13.3033 103403.15 130 13.2792 103413.15 140 13.2553 103423.15 150 13.2314 103425 151.85 13.23 104471 197.85 13.12 104519 245.85 13.00 104571 297.85 12.88 104633 359.85 12.73 104681 407.85 12.61 104691 417.85 12.60 95,100693 419.85 12.60 95,100715 441.85 12.59 95,100758 484.85 12.45 95,100787 513.85 12.35 95,100838 564.85 12.25 95,100900 626.85 12.11 95,100930 656.85 12.02 95,100979 705.85 11.86 95,100
Physicochemical Properties of Metallic Mercury 15
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The temperature, pressure, density and structure of liquid mercury have beenmeasured at elevated temperatures and pressures.118–120 The results arepresented in Table 1.17.
A graphical representation of the density from room temperature to thecritical point is given in Figure 1.8.121
The influence of pressure (up to 800MPa) on the density of mercury in thetemperature ranges 303.15–423.15K,103 400–1833K116 and up to 1723K124 hasbeen studied The isotherms of mercury density versus pressure are shown in
Figure 1.7 Density of solid and liquid mercury versus temperature.15,31,95,97–104
Table 1.15 Change in the volume of mercury duringsolidification (DV¼Vliquid – Vsolid).
DV (%) Ref.
3.59 313.66 1143.67 99
Table 1.16 Density of gaseous mercury.117
T (K) T (1C) r (g cm–3)
968 694.85 0.1211040 766.85 0.1851096 822.85 0.251163 889.85 0.3351263 989.85 0.531346 1072.85 0.851445 1171.85 1.051523 1249.85 1.40
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Figure 1.9. It can be seen that the course of the isotherms becomes morecomplicated at high pressures. These effects are due to changes in the physi-cochemical properties of metallic mercury.116,124
1.11 Surface Tension
Nizhenko and Floka125 and Wilkinson126 summarized the large amount ofexperimental data on the surface tension of mercury (sHg) and amalgams.125
Depending on the experimental conditions (purity of mercury, temperature,gaseous atmosphere, measurement method, etc.), the surface tension
Figure 1.8 Density (r) of liquid and gaseous mercury as a function of temperature upto the critical point (C.P.).Adapted from Refs. 95, 122, 123.
Table 1.17 Temperature, pressure and density of liquid mercury.
T (K) T (1C) P (bar) r (g cm–3) Ref.
293 20 5 13.55 118523 250 49 12.98 118773 500 55 12.42 1181073 800 157 11.56 1181273 1000 405 10.98 1181373 1100 610 10.67 1181473 1200 830 10.26 1181573 1300 1137 9.81 1191623 1350 1325 9.53 1191673 1400 1570 9.25 1191723 1450 1750 8.78 1191773 1500 1980 8.26 1191803 1530 1970 6.5 119
Physicochemical Properties of Metallic Mercury 17
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of mercury changes from 470 to 497 dyn cm–1 (mNm–1). According toSmithells,127 at the melting point of mercury sHg¼ 498 dyn cm–1 and thetemperature coefficient is ds/dT¼ –0.20 dyn cm–1 K–1. Nizhenko and Floka125
recommended values of sHg¼ 497 dyn cm–1 and ds/dT¼ –0.281 dyn cm–1K–1.It follows from the data presented by Wilkinson126 that the conditions of theexperiment have a critical impact on the value of the surface tension. Analysisthat involved almost 200 independent measurements showed that the surfacetension is a normal distribution with a mean close to 466.3� 33 dyn cm–1. Theexperimental values of sHg ranged from 359 to 563 dyn cm–1. In vacuumand dry air, the surface tension of mercury at 298.15K was found to be475.5� 10 dyn cm–1.126 The relationship between surface tension and theatomic and thermodynamic properties of metals, including mercury andamalgams, has been discussed.128,129
1.12 Viscosity
The dynamic viscosity of mercury, Z, is 1.56� 0.015mPa s at 293K.106,130 Itsdependence on temperature can be calculated by means of an Arrhenius-typeequation such as
Z ¼ B expð�E=RTÞ ð1:18Þ
Figure 1.9 Density of pure mercury versus pressure at selected temperatures.Reproduced with kind permission from Deutsche Bunsen-Gesellschaft,G. Schonherr and F. Hensel, Ber. Bunsenges Phys. Chem., 1981, 85(5),361–367. Ref. 116.
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where B¼ 0.560541mPa s and E¼ 2483.137 Jmol–1. According to Vukalovichet al.,45 the temperature dependence of dynamic viscosity in the range623–898K is described by more sophisticated equations.
Kinematic viscosity is calculated based on the dynamic viscosity data bymeans of the equation
v ¼ Zr
ð1:19Þ
where r is the density of mercury at the selected temperature. According toKozin et al.,131 kinematic viscosity depends linearly on the reciprocal oftemperature.
The viscosity of liquid and gaseous mercury at high temperature (up to1520K) and high pressure was studied by Tippelskirch et al.117 using aviscometer with an oscillating cylinder. The amplitude of the cylinder oscil-lations was measured with a helium–neon laser. The viscosity of liquid andgaseous mercury was measured along the saturation line up to 1520K over arange of pressures. Data from the experiments of Tippelskirch et al.117 andfrom other studies131–135 are compared with the theoretical curve using themodified Enskog equations describing the overall saturation zone. Goodagreement between the calculated curves and the experimentally obtainedpoints was observed. The upper curve represents the viscosity of metallicmercury and the lower curve the viscosity of gaseous mercury. The viscosityaround the critical temperature is shown with dashed lines. Tippelskirchet al.117 correlated the calculated curves of the temperature dependence ofviscosity for mercury, sodium and lead with experimental results and observedgood agreement between the data. The viscosity of liquid mercury lies betweenthe values for the other two metals (ZNaoZHgoZPb).
Viscosity values for mercury are given in Table 1.18. Further experimentalinvestigations of the viscosity have been reported elsewhere.136,137
1.13 Isothermal Compressibility
The effect of pressure on the compressibility of mercury at high temperatureswas studied by Schonherr and Hensel.116 Figure 1.10 shows isothermalcompressibility coefficients at different temperatures and constant pressure.At temperatures above 1400K, the compressibility increases abruptlyaccording to the equation
w ¼ 1
d qr=qPð ÞT� 1010 Pa�1 ð1:20Þ
At high temperatures (41400K) and pressures of B9 kgm–3, a metal–non-metal transition is observed. This transition alters the interatomic forcesand increases the isothermal compressibility coefficient. Isothermalcompressibility values for mercury were summarized by Holman and tenSeldam.138
Physicochemical Properties of Metallic Mercury 19
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1.14 Thermal Expansion Coefficient
An equation for the isobaric volume thermal expansion coefficient, a, taken fromBeattie et al.,139 refitted by Ambrose140 for temperatures in 1C on the ITS-90temperature scale, and later refitted for temperatures in K on the ITS-90,138 is
�a ¼182:3887� 10�6 � 1:01689� 10�8T þ 2:2231� 10�11T2
þ 1:5558� 10�14T3ð1:21Þ
Table 1.18 Viscosity of mercury at different temperatures.131,132
T (K) T (1C) Kinematic viscosity (cSt) r (g cm–3) Viscosity (cP) Ref.
623 350 0.070 131573 300 0.072 131523 250 0.076 131513 240 0.0783 13.02 1.02 132503 230 0.0791 13.04 1.03 132493 220 0.0798 13.07 1.04 132483 210 0.0805 13.09 1.05 132473 200 0.080 131473 200 0.0812 13.11 1.06 132463 190 0.0821 13.14 1.07 132453 180 0.0829 13.16 1.09 132443 170 0.0840 13.18 1.10 132433 160 0.0851 13.21 1.12 132423 150 0.086 131423 150 0.0863 13.23 1.14 132413 140 0.0877 13.26 1.16 132403 130 0.0891 13.28 1.18 132393 120 0.0906 13.30 1.20 132383 110 0.0922 13.33 1.22 132373 100 0.094 131373 100 0.0939 13.35 1.25 132363 90 0.0957 13.38 1.28 132353 80 0.0976 13.40 1.30 132348 75 0.099 131343 70 0.0998 13.42 1.33 132333 60 0.102 13.45 1.37 132323 50 0.104 131323 50 0.105 13.47 1.41 132313 40 0.108 13.50 1.45 132303 30 0.111 13.52 1.50 132298 25 0.110 131293 20 0.115 13.55 1.55 132283 10 0.119 13.57 1.61 132273 0 0.123 13.60 1.68 132263 –10 0.129 13.62 1.76 132253 –20 0.135 13.64 1.84 132243 –30 0.141 13.67 1.93 132238 –35 0.145 13.68 1.98 132235 –38 0.147 13.69 2.02 132
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where T is in K and a is in K–1. This equation is valid only at ambient pressurefor the temperature range 253–573K. Liquid mercury expands considerablymore than solid mercury with increase in temperature, its expansion beingdescribed by
vT2¼ vT1
1þ bDTð Þ ð1:22Þ
where vT1and vT2
are the volume of liquid mercury at T1 and T2, respectively,
DT¼T2 – T1 is the temperature difference and b is the coefficient of volumetricexpansion, equal to 0.181�10–3K–1.
1.15 Self-diffusion
Coefficients of mercury self-diffusion and diffusion of metals in mercury can becalculated from Arrhenius equations similar to
D ¼ D0expED
RT
� �cm2 s�1 ð1:23Þ
where D0 is the pre-exponential factor, which has a constant value for the metalbeing studied, and ED is the activation energy. Different authors have reporteddifferent values for ED and D0, as shown in Table 1.19.
These data suggest that values of ED are determined with an accuracy of only25–38% and values of D0 with the accuracy of only 14–48%. The lack ofaccuracy of D0 is caused by both the specifics of the experiment in a broadrange of temperatures, under conditions that rule out convective diffusion, and
Figure 1.10 Isothermal compressibility, wT, of pure mercury.Reproduced with kind permission from Deutsche Bunsen-Gesellschaft,G. Schonherr and F. Hensel, Ber. Bunsenges Phys. Chem., 1981, 85(5),361–367. Ref. 116.
Physicochemical Properties of Metallic Mercury 21
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the need for extrapolating D0 from the plot of lnD versus 1/T to 1/T-0. Datarelating the effect of temperature on the self-diffusion coefficient of mercuryhave been published.142,145–147 Table 1.20 gives values for DHg in thetemperature range 273–566K.
A least-squares analysis of experimental results showed that the self-diffusioncoefficient of mercury is described by Equation (1.24) with D0¼ 1.8601�10–4cm2 s–1 and ED¼ 6005.1 Jmol–1. Efforts were made to calculate ED based oncorrelations between ED and T, ED and DHmelt and ED and DHevap.148–152 Thevalues of ED obtained agree with the experiments.149,151
To calculate diffusion coefficients of metals in mercury, the well-knownequation of the hydrodynamic mass transfer theory is used, where the motion
Table 1.19 Self-diffusion constants for pure mercury.
ED (kJ mol–1) D0 (cm2 s–1) T (K) Ref.
5.104 1.40�10–4 238–533 1416.820 1.63�10–4 273–568 1424.853 1.26�10–4 275.5–364.2 1434.205 0.85�10–4 273–371 144
Table 1.20 Self-diffusion of liquid mercury.
T (K) 1/T (K–1) D �105 (cm2 s–1) Ref.
373 0.002681 2.62 145423 0.002364 3.31 145473 0.002114 4.08 145523 0.001912 4.91 145566 0.001767 5.68 145273.2 0.003660 1.50 142273.2 0.003660 1.51 142315.4 0.003171 1.88 142315.4 0.003171 1.88 142315.4 0.003171 1.89 142352.6 0.002836 2.44 142352.6 0.002836 2.33 142381.6 0.002621 2.69 142381.6 0.002621 2.71 142381.6 0.002621 2.72 142381.6 0.002621 2.77 142414.2 0.002414 3.26 142415.1 0.002409 3.23 142452.9 0.002208 3.80 142497.6 0.002010 4.42 142512.5 0.001951 4.70 142283 0.003534 1.436 147298 0.003356 1.59 147313 0.003195 1.745 147333 0.003003 1.949 147308 0.003247 1.86–1.89 146
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of a macroscopic ball with a radius r-N is traced in a non-compressivemedium having viscosity Z:148,153
D ¼ kT
6pZrð1:24Þ
where Z is the dynamic viscosity of the medium and k is the Boltzmannconstant. This equation is known as the Stokes–Einstein relation and isapplicable, strictly speaking, to ideal solutions where no strong interaction ofdiffusing particles and the medium is observed. Mercury shows a strong affinityto many metals and forms intermetallic compounds (see Appendix I). Hencethe size of the diffusing particle will depend on the nature of the metal. Ithas been shown149,151,153,154 that when the particle diameter d-N, theexperimental data are better described by the equation
D ¼ kT
4pZr¼ RT
NMei�4pZrð1:25Þ
However, this equation requires knowledge of the nature of diffusing particles(atom, ion, associate, intermetallic molecule) and the sizes of the particles.Methods for modification of eqns (1.30) and (1.31) depending on the ratiobetween sizes of the diffusing particle and atoms of the solvent, and also otherfactors, have been discussed.149,155 It was shown that the experimental data onself-diffusion coefficients are fairly consistent with the data155–157 obtainedusing the equation
Dc ¼RT
4ffiffiffi2p
Z
� �d
13 M�1
3 N�13 cm2 s�1 ð1:26Þ
where M is the atomic mass and N is Avogadro’s number. When theproperties of mercury are taken into account, eqn (1.32) is converted to theform157
Dc ¼ 4:743�103deff�1 cm2 s�1 ð1:27Þ
where deff (cm) is the effective diameter of diffusing particle, deff ¼ vMe=Nð Þ13,
and vMe is the molar volume of the diffusing metal at T¼ 298 K. According toVukalovich et al.,45 the self-diffusion coefficient of a metal up to a temperatureof 1073 K (800 1C) is expressed by the equation
Dc ¼ 0:9264�10�10 TZcm2 s ð1:28Þ
where Z is the dynamic viscosity, described by
Z ¼ 0:310� 10�3T0:07939exp341:13
T
� �nsm�2 ð1:29Þ
Figure 1.11 shows experimental values of mercury self-diffusion coefficientsfrom Table 1.20. The values of nMe were taken from the literature2,68,158 whencalculating deff. The linear dependence of lnDc on 1/T can be clearly seen.
Physicochemical Properties of Metallic Mercury 23
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Equation (1.29) allows one to calculate the diffusion coefficients of metals inmercury for given values of D0 and ED. Values of D0 and ED for many metalshave been published.2,148,159 A more detailed discussion of the diffusion coef-ficients of metals in mercury is given in Chapter 4.
1.16 Electrical and Magnetic Properties
The specific resistance (resistivity) of mercury (r) depends on its physical stateand structure. The anisotropy of the resistivity of solid mercury can be up to30% lower along the trigonal axis (r8) and up to 30% higher perpendicular tothat axis (r>). The temperature dependence of the resistivity of mercury atT¼ 80–234.321K is described by the equations45
rII ¼ 1:315þ 35:79� 10�3T þ 0:1588�10�3T2 mO cm ð1:30Þ
and
r? ¼ 1:288þ 54:13� 10�3T þ 0:1899�10�3T2 mO cm ð1:31Þ
with an accuracy r0.5%. The temperature coefficient of resistance is 0.92�10–3K–1. Results of resistivity measurements on solid mercury are given in Table 1.21.
Resistivity values for liquid mercury at different temperatures44,124,160–162 aregiven in Table 1.22. At the melting point, a significant change in resistivity isobserved, as shown in Figure 1.12. For liquid mercury at the melting point it isrliq¼ 90.96 mO cm.32 Ratio values are rliq/r8¼ 4.94163 and rliq/r>¼ 3.73,164
and at the melting point rliq/rsolid¼ 4.2 for polycrystalline samples.The resistivity ratio (r>/r8) of mercury at 100 and 200K is 8.60/6.48¼ 1.327 and
19.71/14.82¼ 1.330, respectively.44 The resistivity of liquid mercury was measured
Figure 1.11 Self-diffusion of mercury.142,145–147
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with high accuracy over a broad range of temperatures [234.321–629.88K at apressure of 1 atm (101.325kPa) and up to 1273K following the saturation curve].Liquid resistivity (rliq) is approximated with a polynomial function:45
rr0¼ 1þ 0:88857�10�3 T � 273ð Þ þ 1:0075�10�6 � T � 273ð Þ2
� 0:105�10�9 T � 273ð Þ3 þ 0:2702�10�12 T � 273ð Þ4
þ 1:199�10�15 T � 273ð Þ5
ð1:32Þ
where r0 is the density of mercury at T¼ 273K and P¼ 101.325 kPa and is94.12�10–8Om.
The temperature coefficient of resistivity of mercury (a) at 15 and 273K isequal to 2�10–6 and (0.89–0.92)�10–3K–1, respectively.160 The resistivity ofmercury is higher than that of any other metal except bismuth. Therefore, ithas been used to define the international ohm standard. The effect of pressure
Table 1.21 Resistivity of solid mercury versus temperature.
T (K) T (1C) r (mO cm) Ref.
15 –258.150 0.0188 11577 –196.150 5.8 11589.5 –183.650 6.97 160100 –173.150 7.89 44200 –73.150 18.08 44223 –50.150 12.3 115227.5 –45.650 21.2 115233.8 –39.350 25.5 115234 –39.150 22.0 44
Table 1.22 Resistivity of liquid mercury versus temperature.
T (K) T (1C) r (mO cm) Ref.
234.288 –38.862 90.96 124234.29 –38.860 94.8 44253 –20.150 91 161273 –0.150 94.7 160293 19.850 95.8 160298 24.850 95 162300 26.850 102.0 160323 49.850 98.5 160373 99.850 103.25 160400 126.850 113.0 44473 199.850 114.27 160500 226.850 126.0 160573 299.850 127.0 160600 326.850 137.0 160623 349.850 135.5 160700 426.850 150.0 44
Physicochemical Properties of Metallic Mercury 25
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on the resistivity of mercury was studied by Schonherr and Hensel.116
It was found that at a density of 13.5–11.0 g cm–3, the resistivity of puremercury, kHg, decreased from 1�104 to 3�103O–1 cm–1. In that case, theelectron mean free path, L, is greater than the smallest distance between atomsof mercury, a, and the resistivity decreases abruptly. At a density of mercury of11.0–9.0 g cm–3, L is close to the lattice parameter a and electron transfer is thenobstructed. It was shown in a number of studies that the decrease in the densityof mercury results in changes of properties such as electrical conductivity, wHg,thermal electromotive force and Hall coefficient (the Knight shift is anexception from this rule).
Mercury is diamagnetic; its magnetic susceptibility (w) is a function oftemperature and its physical state:160
T (K) 80.0 293.0 295.5 560.5Physical state Solid Liquid Liquid Liquidw�109 –0.118 –0.167 –0.1681 –0.1637
It has been found that the magnetic susceptibility also depends on the crystalstructure of mercury. The Knight shift for liquid mercury is 2.45%.165
1.17 Hall Coefficient
The Hall coefficient changes insignificantly with temperature. Values of theHall coefficient for liquid mercury in the temperature range from –30 to 210 1Care given in Table 1.23.
Figure 1.12 Temperature dependence of the resistivity of solid44,115,160 and liquidmercury.44,160
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1.18 Superconductivity
The superconductivity of solid mercury has been extensively studied.38,172,173
Mercury is an example of a superconductor that exists in two crystallographicmodifications. The two polymorphs of mercury exhibit nearly ideal super-conducting behavior.38 Schirber and Swenson38 measured critical fieldquantities, Tc, H0 and (@H/@P)T, as a function of temperature for a- and b-Hg.These results and those of other investigators are given in Table 1.24. Inaddition, the coefficient of the electronic specific heat in the normal state, g, wasalso measured by several researchers and results are reported in Table 1.24.Schirber and Swenson also estimated the Gruneisen constant of solid mercuryto be B2.00.38
1.19 Excited-state Properties
The UV emission and corresponding wavelength values for excited electronicstates are as follows:
6s1s0-6pp1 l¼ 184.957 nm
6s1s0-6p3p1 l¼ 253.652 nm
6p3p1-7s3s1 l¼ 435.835 nm
Table 1.23 Measured Hall coefficients of liquid mercury.
T (K) T (1C) R �10–5 (cm31C–1) Ref.
303–483 30–210 –7.6 166243–373 –30–100 –7.46 167,168293–573 20–300 –7.3 169293–473 20–200 –9.3 170293 20 –8.0 171
Table 1.24 Superconducting properties of a- and b-Hg.
Property a-Hg b-Hg Ref.
Tc (K) 4.153� 0.001 3.949� 0.001 384.1540� 0.0010 394.16 40
H0 (G) 412� 1 339.1� 1 38410 172415.40� 0.12 39a
380� 60 40g (mJmol–1K–1) 1.91� 0.05 1.37� 0.04 38
2.04� 0.03 1752.1� 0.1 1761.809� 0.012 39a
1.86 177
aThese values supersede those of Finnemore et al.173
Physicochemical Properties of Metallic Mercury 27
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Excitation energies for reactions of metallic mercury and its ions are
Hg ns2-ns1p1 4.67 eV
Hg21 ndl0-nd9 (nþ 1)s1 5.3 eV
Hg21 ndl0-nd9 (nþ 1)p1 14.7 eV
Figure 1.13 shows a simplified energy level diagram for atomic mercury.
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1991, 3, 4443.119. K. Tamura and S. Hosokawa, Phys. Rev. B, 1998, 58, 9030.120. M. Inui, X. Hong and K. Tamura, Phys. Rev. B, 2003, 68, 094108.121. F. Hensel and E. U. Franck, Rev. Mod. Phys., 1968, 40, 697.122. J. Bender, Phys. Z., 1918, 19, 410.123. F. Hensel and E. U. Franck, Ber. Bunsenges, Phys. Chem., 1966, 70, 1154.124. F. E. Neale, N. E. Cusack and R. D. Johnson, J. Phys. F, 1979, 9, 113.125. V. I. Nizhenko and L. I. Floka, Surface Tension in Liquid Metals and
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lurgiya, Moscow, 1963.129. S. N. Zadumkin, Zh. Eksp. Teor. Fiz., 1953, 24, 615.130. Physikalisch-Technische Bundesanstalt, PTB-Stoffdatenblatter, Queck-
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Bunsenges. Phys. Chem., 1977, 81, 339.138. G. J. F. Holman and C. A. ten Seldam, J. Phys. Chem. Ref. Data, 1994,
23, 807.139. J. A. Beattie, B. E. Blaisdell, J. Kaye, H. T. Gerry and C. A. Johnson,
Proc. Am. Acad. Arts Sci., 1941, 71, 371.140. D. Ambrose, Metrologia, 1990, 27, 245.141. E. F. Broome and H. A. Walls, Trans. Met. Soc. AIME, 1968, 242, 2177.142. R. E. Meyer, J. Phys. Chem., 1961, 65, 567.143. R. E. Hoffman, J. Chem. Phys., 1952, 20, 1567.144. R. E. Norman, N. H. Nachtrieb and J. Petit, J. Chem. Phys., 1956,
24, 746.145. R. P. Chhabra, Met. Trans., 1986, 17A, 355.146. Z. Galus, Pure Appl. Chem., 1984, 56, 635.147. V. M. M. Lobo and R. Mills, Electrochim. Acta, 1982, 27, 969.148. J. R. Wilson, Metall. Rev., 1965, 10, 381.149. B. S. Bakshtein, Diffusion in Metals, Metallurgiya, Moscow, 1978.150. D. K. Belashchenko, Transport Phenomena in Liquid Metals and Semi-
conductors, Atomizdat,Moscow, 1970.151. V. Zayt, Diffusion in Metals, Foreign Literature Publishing, Moscow,
1958.152. I. B. Borovsky, K. P. Gurov, I. D. Marchuk and Yu. E. Uchaste, Inter-
diffusion Processes in Alloys, Nauka, Moscow, 1973.153. A. G. Stromberg and D. P. Semenchenko, Physical Chemistry, Vysshaya
Shkola, Moscow, 1988.154. H. A. Walls and W. R. Upthegrove, Acta Met., 1964, 42, 461.155. B. Ottar, Acta Chem. Scand., 1955, 9, 344.156. G. M. Panchenkov, N. N. Borisenko and V. V. Erienkov, Zh. Fiz. Khim.,
1971, 45, 2338.157. V. N. Korshunov, Amalgam Systems, Structure and Electrochemical
Properties, Moscow University Publishing, Moscow, 1990.158. D. Stull and G. Sinke, Thermodynamic Properties of the Elements,
American Chemical Society, Washington, DC, 1956.159. C. Guminski, in Liquid Metal Systems, ed. H. U. Borgstedt, Plenum Press,
New York, 1995.160. M. E. Drits (ed.), Properties of Elements, Metallurgiya, Moscow, 1985.161. N. W. Ashcroft and J. Lekner, Phys. Rev., 1966, 145, 83.162. R. Evans, D. A. Greenwood, P. Lloyd and J. M. Ziman, Phys. Lett., 1969,
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169. Y. Tieche, Helv. Phys. Acta, 1960, 33, 963.170. E. G. Wilson, Philos. Mag., 1962, 7, 989.171. J. Enderby, Proc. Phys. Soc. (London), 1963, 81, 772.172. I. E. Maxwell and O. S. Lutes, Phys. Rev., 1954, 95, 333.173. D. K. Finnemore, T. Mapother and R. W. Shaw, Phys. Rev., 1960,
118, 127.174. S. J. C. van der Hoeven Jr and P. H. Keesom, Phys. Rev., 1964, 135, A631.175. R. G. Chambers and J. G. Park, in Proceedings of the Seventh Inter-
national Conference on Low Temperature Physics, Toronto, 1960, ed. M.Graham and A. C. Hollis, University of Toronto Press, Toronto, 1960.
176. B. B. Goodman, Proceedings of Kammerlingh-Onnes MemorialConference on Low-Temperature Physics, Leiden, 1958, Physica, 1958,24, S149.
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178. P. van de Weijer and R. M. M. Cremers, J. Appl. Phys., 1983, 54, 2835.179. N. W. Ashcroft and N. D. Mermin, Solid State Physics, Holt, Reinhart
and Wilson, New York, 1976.180. F. Bernhardt, Phys. Z., 1925, 26, 265.181. L. Cailletet, E. Colardeau and C. Riviere, C. R. Acad. Sci., 1900,
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204. O. Ruff and B. Bergdahl, Z. Anorg. Allg. Chem., 1919, 106, 76.205. G. Schonherr and F. Hensel, Ber. Bunsenges. Phys. Chem., 1981, 85, 361.206. D. H. Scott, Philos. Mag., 1924, 47, 32.207. N. G. Schmahl, J. Barthel and H. Kaloff, Z. Phys. Chem., 1965, 46, 183.208. A. Schneider and K. Z. Schupp, Elektrochem. Angew. Phys. Chem., 1944,
50, 163.209. A. Smith and A. W. C. Menzies, J. Am. Chem. Soc., 1910, 32, 1434.210. S. Sugawara, T. Sato and T. Minamiyama, Bull. JSME, 1962, 5, 711.211. M. Volmer and P. Kirchhoff, Z. Phys. Chem., 1925, 115, 233.212. S. Young, J. Chem. Soc., 1891, 59, 629.
Physicochemical Properties of Metallic Mercury 35
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CHAPTER 2
Amalgam Solubility
2.1 Solubility of Metals in Mercury
The properties of mercury and its alloys are essential information for the theoryand application of electrochemistry,1,2 synthesis of semiconducting materials,3,4
metallurgical processes using amalgams to obtain high-purity and super-puritymetals, lighting, the chlor-alkali process, application as a heat-transfer medium,liquid electrical contacts, etc.5–9 Knowledge of the solubility of metals inmercury and the temperature dependence of their solubility is of the utmostimportance for these applications. This chapter discusses predictive models forsolubility and presents extensive data on the measured solubility of metals inmercury.
Various researchers6–16 have contributed critical analyses of studiesdedicated to the solubility of metals in mercury. Currently there are experi-mental data confirming the solubility of 75 metals6–8,17–26 in mercury.Therefore, several authors have developed mathematical relationships betweenthe solubility of metals in mercury and the physicochemical properties of puremetals. The goal is to calculate the solubility of a metal in mercury based on thephysical parameters of the pure metal.6–8,14 These efforts have met with a fairdegree of success. Appendix V gives experimental values for the solubility ofmetals in mercury, and Figure 2.1 shows the solubility of metals in mercury ingraphical form.
The possibility of calculating the solubility of metals in mercury is of greatpractical interest for high-purity mercury production processes. The chemicalpotential of a metal in mercury obeying an ideal solution is expressed by theequation
midealMe ¼ m0 þ RT lnx1 ð2:1Þ
where m0 is the standard chemical potential of the metal in mercury and x1 is themole fraction of the metal dissolved in mercury.
Mercury Handbook: Chemistry, Applications and Environmental Impact
By Leonid F Kozin and Steve Hansen
r L F Kozin and S C Hansen 2013
Published by the Royal Society of Chemistry, www.rsc.org
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For thermodynamic equilibrium (at p, T¼ constant), it is essential that thereis equality of the chemical potentials of metals contained in a saturated mercury
solution (amalgam) m�saturatedMe and the solid metal msolidMe :
midealMe ¼ m�saturatedMe ¼ m0 þ RT lnx�saturated1 ð2:2Þ
For a pure solid metal, msolidMe ¼ m0. In the case of a saturated amalgam that
obeys an ideal solution, after substitution into eqn (2.2), the solubility of the
metal in mercury may be represented, considering that Dm ¼ m�saturatedMe � m0 ¼DG, via a change of Gibbs free energy (DG�saturated1 ):
lnx�saturated1 ¼ m�saturatedMe � m0RT
¼ D �G�saturated1 ð2:3Þ
In the case of formation of ideal solutions (at x1ox�saturated1 ) and
considering that
D �G1 ¼ DHmelt:Me1 � TDSmelt:Me1 ð2:4Þ
eqn (2.3) will appear as
lnx1 ¼DHmelt:Me1
RT� DSmelt:Me1
Rð2:5Þ
where DHmelt:Me1 is the heat of fusion of the metal and DSmelt:Me1 is the entropy
of fusion of metal Me1 to be dissolved in mercury.
Figure 2.1 Solubility of different metals in mercury. References are in Appendix V.Adapted from sources.29,73–89
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The entropy of melting of the metal to be dissolved in mercury may becalculated from DHmelt:Me1 and Tmelt:Me1 , which are known fairly accurately for
many metals:
DSmelt:Me1 ¼DHmelt:Me1
Tmelt:Me1
ð2:6Þ
By substituting eqn (2.6) into eqn (2.5) and simplifying, we obtain the well-known Schroder equation:
lnx1 ¼DHmelt:Me1
R
1
Tmelt:Me1
� 1
T
� �ð2:7Þ
from which it follows that, given an ideal solubility of metals in mercury, thelogarithm of solubility is a linear function when plotted against the reciprocalof temperature. When lnx1 is plotted versus 1/T, the result should be a straight
line with slope DHmelt:Me1
�R. Ideal curves are linear. The difference between the
actual and ideal curves of solubility of metals in mercury lies in their behaviorat low temperatures (T¼ 0.30–0.5Tmelt).
Kozin [7] analyzed the experimental data on the solubility of metals inmercury at different temperatures in terms of compliance with the Schroderequation by plotting lnx1 against 1/T. The following systems were analyzed:In–Hg, Tl–Hg, Cu–Hg, Pb–Hg, Ag–Hg, Au–Hg, Bi–Hg and Sn–Hg. It wasdemonstrated that the curves describing the actual solubility of metals inmercury deviate strongly from the ideal solubility curves, obtained from eqn(2.7). It was concluded that eqn (2.7) cannot be used to calculate the solubilityof metals in actual mercury (amalgam) systems. This is because, in an actualsolution, the chemical potential of the metal dissolved in mercury is
mMe ¼ m0 þ RT lna1 ð2:8Þ
where a1¼ activity of metal Me1 in mercury. As reported,6–8,28,29 the numericalvalue of a metal’s activity in an amalgam is determined by the choice of thestandard state. To facilitate the analysis of the deviation of the behavior of amercury solution from ideal behavior, it is best to choose the pure metal for astandard state. The activity coefficient, g, is used for a quantitative assessmentof how much an amalgam deviates from ideal solution parameters:
g1 ¼a1
x1ð2:9Þ
or
a1 ¼ g1x1 ð2:10Þ
By substituting eqn (2.10) in eqn (2.8), we obtain
mMe1¼ m0 þ RT lng1ð Þx1 ð2:11Þ
By subtracting eqn (2.1) from eqn (2.11), we obtain
mMe1� midealMe ¼ RT lng1 ð2:12Þ
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Considering that the activity coefficient g1 is functionally dependent on thepartial excess Gibbs free energy:
�Gexcess ¼ RT lng1 ð2:13Þ
and taking into account the equation
�Gexcess ¼ D �Hmix � TDSexcessmix ð2:14Þ
we may use equations (2.12)–(2.14) to deduce
RT lng1 ¼ D �Hmix � TDSexcessmix ð2:15Þ
The atomic interaction between metals and mercury in concentratedamalgams may produce compounds MeHgn or solid solutions MexHgy. In thiscase, eqn (2.11) may be represented as
m�saturatedMe1¼ m0 þ RT lng1x1 ð2:16Þ
The change in chemical potential, Dm, for a saturated amalgam is
Dm ¼ m�saturatedMe1� m0. Keeping in mind eqns (2.3)–(2.16), we obtain
lnx1 ¼DHmix;Me1
RT� DSmelt;Me1
T
� �� D �Hmin � TD �Smelt
mix
RT
� �ð2:17Þ
From classical thermodynamics,
D �Sexcess ¼ D �Smix � D �Sideal ð2:18Þ
and
D �Sideal ¼ RT lnx1 ð2:19Þ
where D �Smix is the partial molar entropy of mixing in an actual solution
and D �Sideal is the ideal entropy of solution. Combining eqns (2.17)–(2.19), weobtain
lnx1 ¼DHmelt:Me1 � TDSmelt:Me1 � D �Hmix þ TD �Smix � TD �Sideal
RTð2:20Þ
For easier analysis, eqn (2.20) may be converted into
lnx1 ¼DHmelt:Me1
R
1
Tmelt:Me1
� 1
T
� �� D �Hmix � TD �Smix þ TD �Sideal
RT
� �ð2:21Þ
For the case where D �Hmix ¼ 0 and D �Smix ¼ D �Sideal, the solubility of a metalin mercury is described by the Schroder equation [the first member on the right-hand side of eqn (2.21)]. Therefore, the first term on the right-hand side of eqn(2.21) corresponds to the solubility of a metal in an ideal mercury solution
(lnxideal1 ), whereas the second term characterizes the deviation from the ideal
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metal behavior in a mercury solution (lng1). Therefore, eqn (2.21) may berepresented as7
lnx1 ¼ lnxideal1 � lng1 ð2:22Þ
or
lnx1 ¼ lnxideal1
g1
� �ð2:23Þ
x1 ¼xideal1
g1ð2:24Þ
Using eqn (2.24), one may calculate the solubility of a metal in any givensystem once the activity coefficients of the components are known, and viceversa, if x1 and x1
ideal are known, one may calculate the activity coefficients ofthe metals present in a system. Equations (2.21)–(2.24) describe the solubilityof a metal in mercury irrespective of its liquid phase state, such as the formationof associates. Analysis of eqns (2.22) and (2.24) indicates that for g141 thesolubility is less than the ideal solution and for g1o1 the solubility exceeds theideal solution. At g1¼ 1 the solubility obeys an ideal solution. Consequently, tocalculate the solubility of metals in mercury from eqns (2.20)–(2.24), we needdata describing the thermodynamic properties of metals in amalgams:DHfusion,Me1 , DHmix, DSfusion,Me1 , DSmix or g1.
2.2 Amalgams with Compounds Formed in the
Solid Phase
The temperature dependence of the solubility in mercury of In, Tl, Cd, Zn, Na,Cs, Li, K, Bi, Sn, Pb, Au, Ag, Sm, Pu, Cu, Mn, U, Th, Sb, Ni, Ti, Be, Zr, Cr, Coand Fe has been reported.6–8,11–26 Many metals that are poorly soluble inmercury, except Th, Sb and Be, feature the same slopes of their curves of lnx1versus 1/T. This indicates that these metals should have close heat of solutioneffects in mercury. Low melting point metals demonstrate different slopes of thecurves in question (In, Tl, Cd, Zn, Na, Cs, Li, K, Ga, Bi, Sn, Pb). The solubilityof metals in mercury depends on their nature and may vary by 10 orders ofmagnitude (compare x1 of indium and iron, indium and cobalt, etc.). The actualsolubility curves of compound-forming metals such as nickel, manganese, silverand lead at the decomposition temperatures of the peritectic reactions featuredistinct breaks, which, according to Jangg and Palman,30 are due to variationsof the activity coefficients of the metals present in the solution. Jangg andPalman30 suggested the following empirical equation for the formation ofcompounds in a mercury solution:
lnx1 ¼DHfusion � TDSfusion þ a DHform � TDSformð Þ � DHmix
RTð2:25Þ
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where DHform and DSform are enthalpy and entropy, respectively, of theformation of a mercury compound or associate, DHmix is the enthalpy ofmixing between compound and mercury and a is the degree of dissociation ofcompound in the mercury phase [note that in eqn (2.25) we have replaced thethermochemical system of notations used in Ref. 26 with a thermodynamicsystem]. The third term on the right-hand side of eqn (2.25) corresponds tochange of Gibbs free energy in the course of compound formation:
DGform ¼ a DHform � TDSformð Þ ð2:26Þ
Table 2.1 gives values for the melting point, boiling point, enthalpy ofmelting and enthalpy of vaporization for about 50 different metals.
Nickel forms several compounds with mercury. One compound, NiHg4, isstable at temperatures up to B224 1C (497 K) and is present as a solid residueand as a dissolved non-dissociated compound:
ðNiHg4Þx"ðNiHg4Þx�m þmNiHg4 ð2:27Þ
According to Jangg and Palman,30 at temperatures below the peritectic point,the degree of dissociation of NiHg4 makes no major changes and makes thelnx1 versus 1/T curve appear as a straight line. Near the peritectic point, due toincreasing dissociation, the negative member a(DHform – TDSform) becomesprogressively smaller and causes the solubility of the metal in mercury in eqn(2.25) to grow faster than it would as a linear function. At temperatures highabove the peritectic point, a becomes independent of temperature and equal tozero. Therefore, the curves of lnx1 versus 1/T return to linear. In this case, eqn(2.25) reduces to
lnx1 ¼DHfusion;Me1 � TDSfusion;Me1 � DHmix
RTð2:28Þ
However, this equation fails to take into account the excess entropy of mixingDSexcess, which, as seen from eqn (2.18), equals the difference between DSmix
and DSideal. Therefore, eqn (2.28) only applies when the dissolution of a metalin mercury comes with entropy of mixing DSmix equal to DSideal, i.e., when theresulting mercury solution of metal Me1 obeys the laws of regular solutions. Inthis case, the calculated solubilities of metals in mercury obtained from eqn(2.28) should agree with the experimental data.
According to Baranski and Galus,46 the Ni–Hg system produces threecompounds: NiHg4, NiHg3 and NiHg2. NiHg2 is stable up to about 458K,NiHg3 up to 483K and NiHg4 up to 493K. Saturated nickel amalgam is inequilibrium with pure nickel above 493K. Data on the solubility of nickel inmercury are given in Table 2.2.
By examining the lnXNi versus 1/T curve, according to Baranski andGalus,46 with data for nickel and other metals, we found that the solubilityvalues suggested46 are seriously understated (by around two orders of
Amalgam Solubility 41
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Table 2.1 Physicochemical properties of metals.
Element Tmelt (K) Tboil (K) DHfusion (J mol–1) DHvap (kJ mol–1) Ref.
Ag 1234 2436 11 297 283 658 31Al 933.3 2793 10 795 326 921 31Au 1336.2 3130 12 552 368 012 31Ba 1002 2171 7749 182 719 31Be 1560 2745 11 715 320 013 31,32Bi 544.5 1837 11 297 209 849 31Ca 1112 1757 8535 177 749 31Cd 594.2 1040 6192 111 851 31Ce 1071 3716 5460 423 195 31,33Co 1768 3201 16 192 426 847 31Cr 2130 2945 395 342 31,34Cs 301.6 944 2092 77 580 31Cu 1356.6 2836 13 054 335 620 31Fe 1809 3135 13 807 413 111 31Ga 302 2478 5590 270 981 31Gd 1586 3546 10 054 398 932 31,33Ge 1210.4 3107 36 945 371 707 31Hf 2500 4876 15 100 618 881 31,35In 429.8 2346 3264 243078 31Ir 2716 4898 22 490 660 143 31,36K 336.4 1032 2335 90 132 31La 1191 3737 6197 431 303 31,33Li 453.7 1615 3000 157 800 31Mg 922 1363 8954 145 243 31Mn 1517 2335 11 004 282 056 31,37Mo 2890 4912 32 539 656 553 31Na 371 1156 2598 107 345 31Nb 2740 5017 31 100 718 217 31,38Nd 1294 3347 7142 328 473 31,33Ni 1726 3187 17 472 428 078 31Pb 600.6 2023 4799 195 736 31Pd 1825 3237 16 985 375 832 31,39Pr 1204 3793 6887 356 837 31,33Pt 2042 4149 21 330 565 000 31,40Pu 913 3503 2845 352 167 31Rb 312.6 961 2192 82 170 31Rh 2233 4114 27 300 551 840 31,41Sb 904 1860 19 874 264 228 31Sc 1812 3109 14 096 376 112 31Si 1685 3540 50 551 455 638 31Sn 505.1 2876 7029 301 374 31Th 2023 4795 13 817 575 614 31,42Ti 1943 3562 13 000 467 131 31,43Tl 577 1746 4142 181 594 31Tm 1818 2223 16 841 233 413 31,33U 1405 4407 8519 522 866 31V 2183 3682 21 500 510 946 31,44Y 1799 3618 11 397 423 785 31,33Zn 692.7 1180 7322 129 867 31Zr 2125 4682 30 500 607 488 31,45
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magnitude). At higher temperatures, different authors have suggested figuresthat are in close agreement between themselves.11
Let us compare the actual solubility curves with an ideal curve plotted usingeqn (2.7) in coordinates’ of b–lnx1, where
b ¼ DHmelt:Me1
R
1
Tmelt� 1
T
� �
The curves for the solubility of metals in mercury in coordinates of b–lnx1 havebasically the same slope in the dissolved amalgams section and, with theexception of Th, Pt and Mn, run parallel to each other. Of all metals, thesolubility of platinum in mercury is the closest to ideal. We believe that the datafor the Pt–Hg system, agreeing with eqn (2.7), are wrong, as the system
Table 2.2 Solubility of nickel in mercury.
T (K) T (1C) Mole fraction Pt Ref.
293 20 4.8�10�7 30293 20 1.5�10�9 46323 50 1.2�10�6 30323 50 1.8�10�8 46373 100 3.7�10�6 30373 100 4.1�10�7 46423 150 0.0000085 30423 150 0.0000047 46473 200 0.000017 30473 200 0.000030 46498 225 0.000021 30503 230 0.000029 30505 232 0.000032 30507 234 0.000034 30509 236 0.000038 30516 243 0.000041 30523 250 0.000044 30573 300 0.000075 30623 350 0.00011 30673 400 0.00015 30723 450 0.00019 30773 500 0.00022 30773 500 0.00030 47773 500 0.0013 47823 550 0.00035 47885 612 0.00043 47898 625 0.00024 47923 650 0.00066 47938 665 0.0041 47973 700 0.00055 47973 700 0.00099 47998 725 0.0012 471023 750 0.00071 471023 750 0.0027 47
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produces compounds PtHg, PtHg2 and PtHg3.48,49 Our calculations7,50 have
shown the solubility of platinum in mercury at 298K to be 3.1�10–7 at.%.Jangg and Dortbudak51 studied the solubility of platinum in mercury from 374to 593K and proved it to increase from 3.14�10–7 to 9�10–6 mole fraction,respectively (Table 2.3). By extrapolating these data in coordinates of lnxPt–1/Tto 298K, we obtained a solubility of platinum in mercury of 1.8�10–6 at.%.This agrees well with the calculated value quoted in the literature.7,50
The actual solubility curves are not parallel to the ideal solubility curve. Thedifference lnx1
ideal – lnx1 becomes less pronounced as the temperature increases.In this case, the activity coefficients of metals in mercury should decrease [seeeqn (2.22)]. The curves of b versus lnx1 vary substantially with temperature nearthe melting point of the metal dissolving in mercury. The metal–mercurysystems approach complete mutual solubility of the components at the meltingpoint of the solute metal. The straightness of b versus lnx1 curves over a broadinterval of temperatures, especially for metals demonstrating poor solubility inmercury, was used to determine accurately the solubility of metals in mercury atdifferent temperatures via our graphical method.
In our analysis of the temperature dependence of the solubility of platinum inmercury in coordinates of b–lnx1, we estimated the solubility of platinum inmercury to be between 3.1�10–7 and 1.8�10–6 at.%. These were obtainedthrough extrapolation of data of Guminski and Galus.11 In our view, the oftenquoted figures for the solubility of platinum in mercury (0.102 at.% at297.15K9,49,53 and 2.8�10–2 at.% at 293K54) fail to reflect the actual solubilityof platinum in mercury. Clearly, the value xPt¼ 5�10–4 at.% quoted in theliterature11,55,56 also overstates the actual solubility of platinum in mercury. It
Table 2.3 Solubility of platinum in mercury.
T (K) T (1C) Mole fraction Pt Ref.
298 25 5�10�6 52374 101 3.14�10�7 51374 101 3.64�10�7 51397 124 7.08�10�7 51397 124 6.96�10�7 51424 151 6.66�10�7 51424 151 8.73�10�7 51445 172 1.13�10�6 51445 172 1.46�10�6 51465 192 1.73�10�6 51465 192 1.10�10�6 51473 200 2.86�10�6 51473 200 3.19�10�6 51523 250 5.51�10�6 51523 250 5.28�10�6 51555 282 7.87�10�6 51555 282 7.71�10�6 51581 308 8.50�10�6 51581 308 8.36�10�6 51593 320 9.06�10�6 51
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will be observed that the solubilities of chromium, cobalt and iron according toKozin7 are much smaller those reported by various other sources,9,17–21 andcorrelates well with other data.55,56
The solubilities of rare earth metals in mercury seem to be understatedcompared with the experimental figures.16 The alkali metals sodium, cesium,lithium and potassium have solubilities of 3.0, 1.51, 0.56 and 0.45 at.%,respectively.6,7
It should be mentioned that the graphical method of finding the solubility ofmetals in mercury through extrapolation in coordinates of b–lnx1, which wasdeveloped earlier,7 has proven very reliable. The solubility values yielded by ourgraphical method were benchmarked against high-precision experimentalsolubility data for copper, gold, manganese and silver. The results demon-strated a very high degree of correlation.
The xMe1 (solubility) values provided for many metals and elements cover
much of the Periodic Table. However, many of those figures are ill-founded,which adds appeal to the calculation methods and allows us to estimate,a priori, the probable solubility in mercury for all known elements. Table 2.4gives a comparison of experimental solubility values and those predicted byeqns (2.29) and (2.30).
Kozin50,57 suggested two equations for finding the probable solubility ofmetals in mercury: one based on the difference between the entropies ofmelting:
lnN1 ¼ �DHmelt:Me1=T � DHmelt:Me1=T� �1:39
1:896¼ DS1:39
1:896ð2:29Þ
Table 2.4 Measured and calculated solubilities of metals in mercury at298.15 K (x, mole fraction).
Element Solubility at 25 1C Ref. 10 Eqn (2.29) Eqn (2.30)
Ag 0.00071 7.6�10–4 – 3.6�10–4Al o0.001 1.6�10–4 1.7�10–3 1.0�10–4Au 0.00467 (80 1C) 1.4�10–3 – 1.2�10–3Bi 0.0112 (22.5 1C) 1.3�10–2 – 1.4�10–2Cd 0.105 (28.5 1C) 9.53�10–2 – (3–4.5)�10–2Co 2.0�10–8 (160 1C) 1�10–9 1.3�10–10 4.5�10–11Cu 0.00006–0.0001 1.0�10–4 6.3�10–5 5.5�10–5Fe 5.4�10–6 o10–9 5.1�10–8 1.6�10–8In 0.70 0.70 – –Mn 4.4�10–5 4.5�10–5 6.7�10–5 (0.07–3.1)�10–4Ni 5�10–7 2�10–9 8.4�10–8 (0.26–3.5)�10–7Pb 0.0165 1.63�10–2 – 6.5�10–3Pd 5�10–5 5.1�10–5 – 3.2�10–5Pt 5�10–6 5�10–6 6.4�10–8 (0.4–6.5)�10–7Pu 0.000161 1.5�10–4 2.0�10–4 4.5�10–4Sn 0.0127 1.26�10–2 – 1.10–4
Tl 0.427 – –Tm 4�10–6 – 3.3�10–6Zn 0.0696 (30 1C) 6.32�10–2 – 1.8�10–2Zr 6�10–8 – 3.6�10–8
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and the other based on the bond energies of the crystalline lattice of thedissolved metal:
lnN1 ¼ �wEMeMe
2:3RTð2:30Þ
where w is a constant equal to 0.414 and EMeMe is the metal–metal bond energy,found from the equation
EMeMe ¼2DHsubl
Jð2:31Þ
where DHsubl is the heat of sublimation and J is the coordination number of themetal’s crystalline lattice.
For the calculation of lnN1 using eqn (2.29), heats of melting DHmelt,Me1
and melting temperatures Tmelt were taken from the literature;31–45,58–63 for thecalculation of interatomic bond energies, published heats of sublimation of themetals were used;58,66 and coordination numbers for solid and liquid stateswere taken from other sources.59,60,64–71
Using melting temperatures and enthalpies of melting and sublimation,one can use eqns (2.29) and (2.30) to calculate likely solubility of metals inmercury at 293.15K. The XMe values obtained using these equations aregiven in Table 2.4. For comparison purposes, the table also offers knownexperimental data on the solubility of metals in mercury (columns two andthree). Compared with data in the literature,6–8,72 many calculated XMe1 valueswere updated using more credible published initial parameters (DHmelt.Me1,DHsubl, Tmelt.Me1, J).
As can be seen from Table 2.4, for many metals the theoretical solubilityvalues correlate well with the experimental data. For some metals, owing toinaccurate coordination numbers (different values according to differentauthors), the calculated solubility values are scattered. In this case, thecalculated solubilities obtained using mean coordination numbers demon-strated good correlations with the experimental data. For some low-meltingmetals, such as gallium, indium, thallium, tin and lead, the calculated solu-bilities obtained from eqn (2.30) were extremely low. Clearly, the coordinationnumbers used for these metals were not accurate. According to Lamoreaux,55
elements with predominantly covalent or ionic bonds have coordinationnumbers o8, whereas metals generally have coordination numbers of 8–12.
References
1. L. F. Kozin, Electrodeposition and Dissolution of Polyvalent Metals,Naukova Dumka, Kiev, 1986.
2. L. F. Kozin and A. G. Morachevsky, Physical Chemistry and Metallurgy ofHigh-Purity Lead, Metallurgiya, Moscow, 1986.
3. B. F. Bilenkoy and A. K. Filatova, Mercury Sulfide: Production andApplication, Lvov University, Lvov, 1988.
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4. L. L. Chang and K. Ploog (eds), Molecular-Beam Epitaxy and Hetero-structures, Nijhoff, Moscow, 1985.
5. K. Kutzsche, Neue Hutte, 1989, 34, 189–190.6. L. F. Kozin, Physicochemical Basics of Amalgam Metallurgy, Nauka,
Alma-Ata, 1964.7. L. F. Kozin, Amalgam Pyrometallurgy, Nauka, Alma-Ata, 1973.8. L. F. Kozin, R. Sh. Nigmetova and M. B. Dergacheva, Thermodynamics of
Binary Amalgam Systems, Nauka, Alma-Ata, 1979.9. M. T. Kozlovsky, A. I. Zebreva and V. P. Gladyshev, Amalgams and Their
Application, Nauka, Alma-Ata, 1971.10. C. Guminski, J. Mater. Sci., 1989, 24, 2661–2676.11. C. Guminski and Z. Galus, Metals in Mercury, Solubility Data Series, vol.
25, C. Hirayama, Pergamon Press, Oxford, 1986.12. L. F. Kozin, Proc. Inst. Org. Catal. Electrochem. Acad. Sci. Kazakh. SSR,
1972, 3, 3–30.13. K. K. Lepesov and L. F. Kozin, Proc. Inst. Org. Catal. Electrochem. Acad.
Sci. Kazakh. SSR, 1984, 24, 28–54.14. L. F. Kozin, Physicochemical Research of Amalgam Methods Used to
Obtain High-purity Metals: Synopsis of Thesis, Doctorate of ChemicalSciences, Alma-Ata, 1964, p. 35.
15. L. F. Kozin, Amalgam Metallurgy, Tekhnika, Kiev, 1970, p. 272.16. V. P. Shvedov, A. Z. Frolkov and G. D. Nikitin, Radiokhimii, 1971, 13,
252–255.17. M. Hansen and K. Anderko, Constitution of Binary Alloys, McGraw-Hill,
New York, 1958.18. R. P. Elliott, Constitution of Binary Alloys, First Supplement, McGraw-
Hill, New York, 1965.19. F. A. Shunk, Constitution of Binary Alloys, Second Supplement,
McGraw-Hill, New York, 1969.20. G. Petot-Ervas, C. Petot and E. Bonnier, Bull. Soc. Chim. Fr., 1968, 10,
3972–3975.21. O. A. Barabash and Y. N. Kovalev, Structure and Properties of Metals and
Alloys, Naukova Dumka, Kiev, 1986.22. M. E. Drits and L. L. Zusman, Alloys of Alkali and Alkaline-Earth Metals
in Mercury, Metallurgia, Moscow, 1986.23. V. S. Fomenko, Emission Properties of Materials, Naukova Dumka, Kiev,
1981.24. W. H. Young, Can. J. Phys., 1987, 65, 241–265.25. K. Hain and E. Burig (eds), Solidification from Melts: a Handbook,
Metallurgia, Moscow, 1987, p. 320.26. S. Tamaki, Can. J. Phys., 1987, 65, 286–308.27. M. B. Dergacheva and L. F. Kozin, Zh. Fiz. Khim., 1977, 51,
417–420.28. O. F. Devero, Problems of Metallurgical Thermodynamics, Metallurgia,
Moscow, 1986.29. G. Jangg and H. Palman, Z. Metallkd., 1963, 54, 364–369.
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30. R. Hultgren, P. D. Desai, D. T. Hawkins, M. Gleiser and K. K. Kelley,Selected Values of the Thermodynamic Properties of the Elements, AmericanSociety for Metals, Metals Park, OH, 1973.
31. A. J. Stonehouse, J. Vac. Sci. Technol. A, 1986, 4, 1163.32. K. A. Gschneidner Jr and L. Eyring (eds), Handbook on the Physics and
Chemistry of Rare Earths, Elsevier, Amsterdam, 1993, Cumulative Index,vol. 1–15, pp. 509–521.
33. S. V. Lebedev, A. I. Savvatimskii and Yu.B. Smirnov,High Temp., 1971, 9,578–581.
34. P.-F. Paradis, T. Ishikawa and S. Yoda, Int. J. Thermophys., 2003, 24, 239.35. L. B. Hunt, Platinum Group Met., 1987, 31, 32–41.36. S. Sato and O. J. Kleppa, J. Chem. Thermodyn., 1979, 11, 521.37. A. Cezairliyan and J. L. McClure, Int. J. Thermophys., 1987, 8, 577.38. C. Cagran and G. Pottlacher, Platinum Met. Rev., 2006, 50, 144.39. A. K. Chaudhuri, D. W. Bonnell, L. A. Ford and J. L. Margrave, High
Temp. Sci., 1970, 2, 203.40. J. W. Arblaster, Platinum Met. Rev., 1996, 40, 62.41. W. Stoll, Thorium and Thorium Compounds. Ullmann’s Encyclopedia of
Industrial Chemistry, Wiley-VCH, Weinheim, 2000.42. J. L. McClure and A. Cezairliyan, Int. J. Thermophys., 1992, 13, 75.43. J. F. Smith, Bull. Alloy Phase Diagr., 1981, 2, 40.44. O. J. Kleppa and S. Watanabe, Met. Trans., 1982, 13B, 391.45. A. Baranski and Z. Galus, J. Electroanal. Chem., 1973, 48, 289–305.46. J. R. Weeks, Corrosion, 1967, 23, 98–106.47. A. R. Miedema, P. F. De Chatel and F. R. De Boer, Physica, 1980, 101
BþC, 1–28.48. I. N. Plaksin and N. A. Suvorovskaya, Zh. Fiz. Khim., 1941, 15, 978–980.49. L. F. Kozin, Izv. Akad. Nauk Kazakh. SSR, Ser. Khim., 1972, (3), 34–49.50. G. Jangg and T. Dortbudak, Z. Metallkd., 1973, 64, 715–719.51. C. Guminski, H. Roslonek and Z. Galus, J. Electroanal. Chem., 1983,
158, 357.52. E. Bauer, H. Nowotny and A. Stempfl,Monatsh. Chem., 1953, 84, 211–212.53. J. H. Butler and A. C. Makrides, Trans. Faraday Soc., 1964, 60, 938–946.54. R. H. Lamoreaux, Melting Point, Gram-Atomic Volumes and Enthalpies of
Atomization for Liquid Elements, US Energy Research DevelopmentAgency Report LBL-4995, Lawrence-Berkeley Laboratory, Berkeley, CA,1976. Available online at http://www.osti.gov/energycitations/servlets/purl/7273452-6b48Ir/7273452.pdf. Accessed June 13, 2013.
55. A. K. Niessen, F. R. De Boer and R. Boom, et al., CALPHAD: Comput.Coupling Phase Diagrams Thermochem., 1981, 7, 51–70.
56. L. F. Kozin, Physical Chemistry and Metallurgy of High-Purity Mercuryand Its Alloys, Naukova Dumka, Kiev, 1992.
57. G. V. Samsonov, Properties of the Elements (Handbook), Metallurgiya,Moscow, (1976), part 1, p. 810.
58. K. J. Smittles, Metals Handbook, Metallurgia, Moscow, 1980.
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59. O. Kubaschewski and C. B. Alcock, Metallurgical Thermochemistry,Metallurgia, Moscow, 1982.
60. K. Saito, S. Hayakawa, F. Takei and H. Yamadera, Chemistry and thePeriodic Table, Iwanami Shoten, Tokyo, 1979.
61. D. R. Stull and G. C. Sinke, Thermodynamic Properties of the Elements,Advances in Chemistry, American Chem. Soc., 1956, 18, 800.
62. V. P. Glushko (ed.), Thermal Constants of Substances, Moscow, VINITI,1968–1981, No. 3–10.
63. G. Schulze, Metallophysics, Mir, Moscow, 1971.64. E. M. Sokolovskaya and L. S. Guzei, Metallochemistry, Moscow
University Press, Moscow, 1986.65. L. S. Darken and R. W. Gurry, Physical Chemistry of Metals, McGraw-
Hill, New York, 1953.66. D. R. Wilson, Structure of Liquid Metals and Alloys, Metallurgia, Moscow,
1972.67. D. K. Belashchenko, Transfer Phenomena in Liquid Metals and Semi-
conductors, Atomizdat, Moscow, 1970.68. P. P. Arsentyev and L. A. Koledov, Metallic Melts and Their Properties,
Metallurgia, Moscow, 1976.69. I. Vaseda, Liquid Metals, Metallurgia, Moscow, 1980, pp. 182–193.70. A. R. Ubbelohde, The Molten State of Matter, Metallurgia, Moscow, 1982.71. L. F. Kozin, Electrochem. Solutions Met. Syst.: Proc. Inst.Chem. Sci. Acad.
Sci. Kazakh. SSR, 1962, 9, 101–121.72. J. H. Vernik, Phys. Met. Sci., 1967, 1, 220–277.73. D. R. Hudson, Metallurgia, 1943, 28, 203.74. H. A. Leibhafsky, J. Am. Chem. Soc., 1949, 27, 1468.75. C. J. De Gruyer, Recl. Trav. Chim. Pays-Bas, 1925, 44, 937.76. A. A. Sunier and E. B. Gramkee, J. Am. Chem. Soc., 1929, 51, 1703.77. C. Rolfe and W. Hume-Rothery, J. Less-Common Met., 1967, 13, 1.78. H. C. Bijl, Z. Phys. Chem., 1902, 41, 641.79. R. E. Mehl and C. S. Barrett, Trans. AIME, 1930, 89, 575.80. L. F. Kozin and N. N. Tananaeva, Russ. J. Inorg. Chem., 1961, 6, 463.81. A. S. Moshkevich and A. A. Ravdel, Zh. Prikl. Khim., 1970, 43, 71.82. H. E. Thompson, J. Phys. Chem., 1935, 39, 655.83. P. Dumas, L. Bougarfa and J. Bensaid, J. Phys., 1984, 45, 1543.84. M. M. Haring, M. R. Hatfield and P. T. Zapponi, Trans. Electrochem.
Soc., 1939, 75, 473.85. G. V. Yan-Sho-Syan, M. V. Nosek, N. M. Semibratova and
A. E. Shalamov, Tr. Inst. Khim. Nauk Akad. Nauk Kazakh. SSR, 1967,15, 139.
86. G. Petot-Ervas, M. Gaillet and P. Desre, C. R. Acad. Sci., 1967, 264, 490.87. N. A. Puschin, Z. Anorg. Allg. Chem., 1903, 36, 210.88. N. A. Pushin, Z. Anorg. Chem., 1903, 34, 201.89. E. Cohen and K. Inouye, Z. Phys. Chem., 1910, 71, 625.
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CHAPTER 3
Diffusion of Metals in Mercury
3.1 Effect of Atomic Size on Diffusion
The most commonly used equation to calculate the diffusion coefficients ofmetals in mercury is
DMei ¼kT
ApZrMei
ð3:1Þ
where k is the Boltzmann constant (1.38�10–23 JK–1), Z is the dynamic viscosityof pure mercury and rMei is the radius of the diffusing particle. Equation (3.1) is
the so-called Stokes–Einstein (if A¼ 6) or Einstein–Sutherland (if A¼ 4)relation. Along with an A value, the size of the diffusing particle is thesubject of discussion when experimental data are analyzed.1–18 Accordingto Stromberg and Zakharova1 and Gladyshev,2 the theory best agrees withthe experiment when A¼ 6 and when rMei is equal to the ionic radius of the
diffusing metal. According to Zakharov,3 also the metallic one. Galus7 andMa et al.4 preferred the use of A¼ 4.
If A¼ 4, the experimental values obtained for some metals (Pb, Bi, In, Sb,Hg, Sn, Cd, Ga, Zn4–7) match well with those predicted by theEinstein–Sutherland relation. Experimental data concerning the diffusioncoefficients of metals in mercury (system Mei–Hg) have been reported.1–10,19,20
Table 3.1 lists values of DMei obtained mostly from Guminski,19 amended only
for Zn,4 Cd, Hg8 and Ca.10 As can be seen, the values of DMei depend on the
nature of the metal and are at a minimum for La (5.0�10–6 cm2 s�1) and at amaximum for Zn (1.67–1.89�10–5 cm2 s�1).
To demonstrate how the values are affected by the size factor, Figure 3.1
shows the experimental data (Table 3.1) in coordinates of 1=DMei � r0Mei, where
r0Meiis the ionic radius of a metal.11
Mercury Handbook: Chemistry, Applications and Environmental Impact
By Leonid F Kozin and Steve Hansen
r L F Kozin and S C Hansen 2013
Published by the Royal Society of Chemistry, www.rsc.org
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3.1.1 Effect of Atomic Radius
From Figure 3.1, it follows that only a limited number of ‘elementary’ metals,i.e. Fe, Zn, Al, Ga, Ge, Sn, Sb and Bi, fit the theoretical curve of DMei versus
ionic radius within experimental error. Silver, lead, indium and thallium, eventhough they form mercury compounds with only small changes in free energy,demonstrate slight deviations from the theoretical curve.
Alkali metals (Li, Na, K, Rb, Cs), lanthanides (La, Sm, Nd, Tb, Pr, Ce),alkaline earth metals (Ca, Mg, Sr, Ba) and metals marginally soluble in mercury(Ni, Co, Mn, Cu, Ag, Sb) have DMei values that are smaller than those found
from eqn (3.1) with A¼ 4 and correlate with the atomic radius of the metal.
Table 3.1 Diffusion coefficients r0Meiof metals in mercury at 298K, effective
atomic/ionic radii and radii of particles diffusing in mercury phasecompared with those existing in liquid and solid phases of theconstitution diagram.
Element DMei�105 (cm2 s–1)19 reffMei
(nm)19 r0Mei(nm)8 rdiffMei
(nm) DrMei (nm)
Ag 1.05� 0.03 0.127 0.16 0.212 0.052Al 1.6� 0.2 0.126 0.125 0.138 0.013Au 0.85� 0.04 0.126 0.135 0.256 0.121Bi 1.35� 0.1 0.162 0.16 0.16 0.00Ca 0.69 (283K) 0.172 0.18 0.314 0.134Cd 1.64–1.53� 0.03 0.137 0.155 0.155 0.00Ce 0.60� 0.06 0.161 0.185 0.41 0.225Co 0.84� 0.04 0.11 0.135 0.42 0.285Cs 0.65� 0.1 0.24 0.26 0.338 0.078Cu 1.00� 0.08 0.112 0.155 0.218 0.063Fe 1.84� 0.13 0.112 0.14 0.12 –0.020Ga 1.64� 0.08 0.133 0.13 0.136 0.006Hg 1.59–1.60� 0.05 0.143 0.15 0.15 0.00In 1.38� 0.l 0.146 0.155 0.164 0.009K 0.79� 0.08 (293K) 0.188 0.22 0.278 0.058La 0.50� 0.05 0.165 0.195 0.442 0.247Li 0.92� 0.1 0.137 0.145 0.21 0.065Mn 0.90� 0.08 0.114 0.14 0.244 0.104Na 0.84� 0.15 0.168 0.18 0.259 0.079Nd 0.78� 0.08 0.16 0.185 0.284 0.099Ni 0.65� 0.03 0.109 0.135 0.342 0.207Pb 1.25� 0.04 0.154 0.18 0.18 0.00Pr 0.60� 0.06 0.16 0.185 0.41 0.225Rb 0.75� 0.08 0.223 0.235 0.291 0.056Sb 1.40� 0.1 0.154 0.145 0.155 0.010Sm 0.52� 0.06 0.158 0.185 0.424 0.239Sn 1.48� 0.04 0.148 0.145 0.164 0.019Sr 0.96� 0.1 (293K) 0.188 0.200 0.310 0.110Tb 0.82� 0.08 0.156 0.175 0.266 0.091Tl 1.05� 0.05 0.151 0.19 0.206 0.016U 0.6� 0.1 0.135 0.175 0.366 0.191Zn 1.67–1.89 0.123 0.135 0.134 –0.001
Diffusion of Metals in Mercury 51
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Figure 3.1 helps to visualize the real radii of particles diffusing in mercury
(rdiffMei). The values obtained are given in column five of Table 3.1. Column six of
Table 3.1 gives the difference rdiffMei� r0Mei
of atomic and ionic potentials,
according to Slater.11 As can be seen, for simple metals, DrMei ¼ rdiffMei� r0Mei
approaches or equals zero. For alkali metals, the value of DrMei is at its
maximum for Li (0.096 nm) and at its minimum for Rb (0.056 nm). DrMei is
somewhat greater for the alkaline earth metals (0.097 nm for Ba, 0.162 nmfor Ca) and the maximum values overall are demonstrated by the rare earthmetals (0.247 nm for La, 0.225 nm for Ce, Pr, with the exception of Nd,
0.099 nm, and Tb, 0.091 nm). For mercury, r0Hg¼ rdiffHg ¼ 0:150 nm, i.e. DrHg¼ 0.
Using the values for DrMei and Na and Hg as an example, one can
examine the composition of the diffusing particle based on the sum of the
radii r0Na¼ 0:180 nm and r0Hg¼ 0:150 nm. Thus, the total radius of a diatomic
NaHg particle equals 0.330 nm, while the calculated radius rdiff ¼ 0:259 nm.However, the NaHg system demonstrates a volumetric compression of 18%as its components react with each other.12 In the case where n¼ 6, thecompression amounts to
DrNaHg¼0:330� 0:259
0:330� 100¼ 21:5%
The value of DrNa–Hg agrees well with experiment. For alkaline earth metals inthe course of intermetallic compound formation, e.g. CaHg, SrHg and BaHg,the compression26 amounts to DrCaHg¼ 4.85%, DrSrHg¼ 11.42% and
Figure 3.1 Graph of 1 =DMei versus ionic radius of diffusing metals, r0Mei, Line,
theoretical curve with A¼ 4; K, experimental values of 1 =DMei .Reproduced with kind permission from r IUPAC, Z. Galus, Diffusioncoefficients of metals in mercury, Pure Appl. Chem., 1984, 56, 635 (Ref. 7).
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DrBaHg¼ 14.5% again when n¼ 6 in Equation 3.1. Therefore, volumetriccompression in these systems increases with transition from Ca to Ba.
For the early lanthanides, La, Ce, Pr and Sm, the values of rdiffMeiexceed
the sum r0Me þ r0Hg� a characteristic of diatomic particles MeiHg (La
rdiffLa ¼ 0:4424 0:340 nm). Clearly, such systems produce stable triatomic
particles (associates) MeHg2 in liquid mercury. Calculated compression valuesDrMeiHg2 calculated for diffusing species LaHg2, CeHg2, PrHg2 and SmHg2 are
as follows, for n¼ 6 in Equation 3.1:
LaHg2 10.7%CeHg2 15.5%PrHg2 15.5%SmHg2 12.6%
The compression values obtained are comparable to those observed for metalsystems with high affinity for each other.26 Values of DrMei for Nd and Tb are
comparable to those for alkali metals. Apparently, Nd and Tb in liquidmercury form diatomic associates NdHg and TbHg. In this case, thecompression calculation produced the results DrNdHg¼ 15:2% and
DrTbHg¼ 18:2%. These data indicate that diffusion in dilute solutions of these
metals in mercury is limited to relatively simple diatomic associates of the typeMeiHg for Li, Na, K, Rb, Cs, Ca, Sr, Mg, Nd and Tb and triatomic associatesfor La, Ce, Pr and Sm.
Concepts for the diffusion of associates, MejHgm,10,13,19 are based on the idea
of solvation of the metal diluted in mercury as put forth by Hildebrand.14
Compression values are small15 for metals whose DMei values show basically
no deviation from the theoretical curve in the coordinates 1=DMei � r0Mei
.
Nigmetova et al.15 demonstrated that alloy formation between mercury andCd, In, Tl, Sn, Pb and Bi results in the following compression values for n¼ 6in Equation 3.1:
Cd 0.31%In 0.46%Tl 0.77%Sn 0.15%Pb 1.07%Bi 1.67%
Hence in the case of ‘elementary’ metals with a weak affinity for mercury,there is only a slight compression. This explains why these components diffusein a mercury solution as atoms. The experimental values for DMei may disagree
with the theoretical values, DMeianalysis, owing to an inaccurate account of the
viscosity Z, which takes place in the course of the electrolysis of the systemMei(j)–Hg, because the surface concentration of Mei(j) atoms may differ fromthe volume concentration. Indeed, Regel’ and Patyanin22 discovered thephenomenon of surface viscosity: surface layers of Hg, Ca, Na and K, as thickas 10–6 cm, demonstrate viscosity that is one or more orders of magnitudegreater than the viscosity in the mass (volume). The latter is due to differentmolecular order at the surface and in the volume and lower fluidity in the
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surface layer. The above analysis of compression of the atoms of metals andmercury in the course of alloy formation, and also literature data,12,15–17
indicate that associates of metals formed with mercury contain only a limitednumber of atoms. Experimentally determined diffusion coefficients obtained for36 metals have been consolidated.1–7,9,20,31
3.2 Temperature Dependence of Diffusion in Amalgams
Chhabra9 suggested the relation
DMei ¼0:63dHg
� �2BHgRT
2VHg
V � V0
V0
� �
Hg
dHg
dMei
� �ð3:2Þ
for calculating the diffusion coefficients of metals in mercury at differenttemperatures, where BHg is the intrinsic constant of mercury introduced byHildebrand into the fluidity equation (the inverse of viscosity),18 V is the atomicvolume of mercury at zero fluidity, approximately equal to the atomic volumeat its melting temperature, and dHg and dMei are atomic diameters of mercury as
solvent and the diffusing metal, respectively. Chhabra9 consolidated manypreviously known experimental data, especially those related to temperaturedependence, into DMei and compared these with data obtained via eqn (3.2).
The calculations were made using the values of B and V0 for mercury,according to Hildebrand;18 the atomic volumes of mercury at differenttemperatures were calculated from the temperature dependence of its density.Theoretical values obtained for DMei normally exceed the experimental data by
17–99% (for Hg, Ag, Ba, Cd, etc.). Calculated DMei values for cadmium and
potassium in mercury, are compared with the experimental DMei in ref. 7–9, 32.
As can be seen, the most credible experimental values for DMei fit the lines
predicted via the equation
logDMei ¼ logD0Mei�EMei
2:303RTð3:3Þ
where D0 is a pre-exponential factor and EMei is the activation energy for
diffusion of Mei particles. The diffusion coefficient for cadmium isD0,Cd¼ 1.42�10–4 Cm2 s�1 and for potassium D0,K¼ 3.64�10–4 cm2 s�1. Theactivation energies of diffusion for particles of cadmium and potassium are 5.38and 22.21 kJmol–1, respectively.
The temperature dependence of DMei for Ag, Al, Au, Sn, Pb, Zn, Ni and
Sb7,9,31 is not completely clear. For these metals, the function logDMei � 1 =Tmay be only nominally obeyed. The explanation of the discrepancy should lie inthe dependence of DMei values on the experimental conditions. The key factors
affecting DMei are:
1. Purity of the original reagents (no other metallic impurities are allowed).2. Formation of insoluble compounds (since they cause uncontrolled
changes to the analytical signal). The formation of compounds of the
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analyzed metal may take place as the metal in contact with mercurydissolves in it (e.g. Pt and Ag).
3. The use of capillaries of suboptimal sizes for electrochemicalmeasurements. Ma and Kao4 demonstrated that values of DMei increasewith increasing radius of the active electrode and they reach their limit ata certain value Ri. The error in calculating DMei may reach 56% due to
this factor alone.4
4. Convection currents in the capillaries used to determine DMei . Convectioncurrents overstate values of DMei owing to the input from the convective
diffusion coefficient Dconvection. In this case, an experiment is used todetermine the apparent diffusion coefficient (Dapparent), which equals thesum of DMei and Dconvection:
Dapparent¼DMei þDconvection ð3:4Þ
5. The analyzed Mei–Hg systems should be homogeneous and free fromheterogeneous Mei particles.
3.3 Concentration Effects on Diffusion
In theory, the diffusion coefficient should not depend on the concentration ofmetals in the mercury solution (amalgam). However, this condition is true onlyif the concentration of the analyzed metals is very low (Table 3.2). At higherMei concentrations,DMei has been observed to depend on CMei . Indeed, Ravdel
and Moshkevits25 have shown that DPb and DZn decrease as Mei concentrationincreases.
At the same time, according to Ignatova,6 the dependence of DMei (at a
significance level of 0.05) on factors such as electrode radius, r, initial
concentration of metal in amalgam, C0Mei
, time, t, and amalgam viscosity, Z, iscomplex and depends on the nature of the amalgamative metal. Diffusion
coefficients DMei (where Mei¼Cd, Zn, Sb) do not depend on r, C0Mei
or t,whereas DCu depends on C0
Cu and Z.6
Ignatova6 offered a detailed analysis of diffusion coefficients of fivemetals, Cu, Zn, Cd, Sn and Sb, in mercury at 298K (Table 3.3). These values ofDMei are the most credible of all known values. The dependence of DMei on xMei
has also been measured in the Tl–Hg system.34 This system is characterizedby a high solubility of thallium in mercury (43.7 at.%) at 298K (25 1C).The dependence of DTl on xTl was studied using the capillary method with
Table 3.2 Upper and lower limits for concentration-independent diffusion.4
Metal Mei (lower) (mol L–1) Mei (upper) (mol L–1)
Zn 1.6�10–4 2.5�10–2K, Na 5.0�10–5 4.0�10–4Cd 5.0�10–5 1.2�10–2Mn 2.0�10–4 1.3�10–2Cu, Tl 4.5�10–4 2.8�10–3
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radioactive thallium tracer (204Tl). The diffusion coefficient of thallium inthallium amalgam was calculated34 using the equation
Caverage � C1
C1 � C1¼ 8
p2Xn¼1n¼ 0
1
ð2nþ 1Þ2exp
2nþ 1
2l
� �2
p2Dt ð3:5Þ
where Caverage is the average composition of thallium amalgam in a capillarywith filled end and length l (d¼ 1mm, l¼ 3 cm), formed within time t. C1 andCN are the initial concentration of radioactive thallium in the capillary and inthe volume, respectively. Under the experimental conditions described,34
CN¼ 0, so by measuring C1, Caverage, l and t, it is possible to calculate DTl.The diffusion coefficient of thallium decreases in a linear fashion from0.98�10–5 cm2 s�1 at 0.75 at.% to 0.47�10–5 cm2 s�1 at 28.57 at.% thallium.A thallium concentration of 28.57 at.% corresponds to the compound Tl2Hg5detected in liquid amalgam. At xTl 435 at.%, the change of DTl is moderate, yetthe curveDTl–xTl passes through a minimum. The same curve behavior has alsobeen observed in the system K–Hg, in which with increasing concentration ofpotassium in the amalgam, DK decreases and reaches a minimum at xK¼ 33.3at.%.32 Such behavior of DMei demonstrated by thallium and potassium,
according to Galus7 and Guminski,19 indisputably proves the existence of thecompounds Tl2Hg5 and KHg2 in the liquid phase. Earlier we offered otherevidence confirming this point.26–28,35
We should also consider the steady increase of diffusion coefficients DMei
with increasing concentration of diffusing metal Mei. Thus, a study of diffusioncoefficients of indium in the system In–Hg at xIn¼ 3.5–20.0 at.% revealed a risein DIn
36 with increasing amalgam concentration, according to the equation
DIn¼ 2:71� 10�3 1þ 2:66xInð Þexp � 326a
RT
� �ð3:6Þ
Foley and Reid30 suggested that diffusion involves particles that are morecomplex than atoms of indium or ions. Indeed, from the literature,37,38 itfollows that in the In–Hg system the compound InHg6 (Tmelt¼ 257.5K) has, at258 K, already dissociated according to the equation
2InHg6 ! InHg3 þ InHgþ 8Hg ð3:7Þ
Table 3.3 Diffusion coefficients of Cu, Zn,Cd, Sn and Sb at 298 K.6
Metal DMei � 105 (cm2 s–1)
Cu 0.98� 0.05Zn 1.80� 0.06Cd 1.60� 0.007Sn 1.45� 0.026Sb 1.63� 0.007
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The compound InHg6 exists only in the liquid state. Measurements of theelectrical conductivity of indium amalgams26 have shown that InHg3 and InHgare the stable compounds. It has been reported32 that the equilibrium constantof the reaction
InHg3"Inþ 3Hg ð3:8Þ
at 298K is equal to 5.6�10–2 (mole fraction)3. Predel and co-workers33,34
believed that in the In–Hg system there exist structural clusters of the twocompounds InHg2 and InHg. According to others,34 the dissociation constant,kd, of InHg:
InHg"InþHg ð3:9Þ
is 0.26.The system Al–Hg forms a degenerate eutectic phase diagram. Aluminum
does not form compounds with mercury. However, it has been stated41 that thesystem demonstrates an increase in the diffusion coefficient of aluminum withincreasing amalgam concentration.
Table 3.4 gives recommended values of the diffusion coefficient of metals inmercury at ambient temperatures, compiled by Galus.7
3.4 Diffusion of Mercury in Solid Metals
Warburton and Turnbull46 discussed the nature of the diffusion ofnoble and late transition metals in mercury. Diffusion often involves andinterstitial mechanism. Table 3.5 gives the experimental results for mercurydiffusion in Ag, Au, Cu, Pb, Sn and Zn. A diffusion mechanism byinterstitial–vacancy pairs was developed to explain the results of diffusion ofHg in Pb.47
Table 3.4 Diffusion coefficients of metals in mercury (compiled by Galus7).
Metal DM �105 (cm2 s–1) T (1C) Ref.
Ag 1.05 25 36Au 0.85 25 37Bi 1.35 20 38Ce 0.62 25 39Cu 1.00 25 40Ge 1.32 25 41K 0.85 20 5Mg 1.20 25 42Mn 0.94 20 5La 0.50 25 43Pb 1.25 20 44Sb 1.40 25 45Sn 1.48 20 5Zn 1.81 25 40
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Shires et al.48 reported Hg diffusion in the solid amalgam phase Ag2Hg3.They determined the activation energy for volume diffusion to be 30.3 kJmol–1
and the diffusion prefactor to be 1.2�10�4 cm2 s–1 at temperatures between50 and 102 1C. In the same study, the grain boundary diffusion rate constantswere determined as QD¼ 19.1 kJmol–1 and D0¼ 22.8.
References
1. A. G. Stromberg and E. A. Zakharova, Zh. Fiz. Khim., 1966, 40, 81.2. V. P. Gladyshev, Elektrokhimiya, 1971, 7, 1423.3. M. S. Zakharov, Zh. Fiz. Khim., 1965, 39, 509.4. X. S. Ma and H. Kao, J. Electroanal. Chem., 1983, 151, 179.5. A. Baranski, S. Fitek and Z. Galus, J. Electroanal. Chem., 1975,
60, 175.6. L. A. Ignatova, Issled. mech. kin. processes anodnogo rastvoreniya
amalgam organ. ob’ema metodom amalgam. Chronoamperometrii,dissertation Kand. Khim. Nauk, Tomsk, 1978.
7. Z. Galus, Diffusion coefficients of metals in mercury, Pure Appl. Chem.,1984, 56, 635.
8. V. M. M. Lobo and R. Mills, Electrochim. Acta, 1982, 27, 969.9. R. P. Chhabra, Metall. Trans., 1986, 17A, 355.
10. V. N. Korshunov, Amalgam Systems: Equilibrium Potentials of SimpleAmalgams, Izdatelstvo Moskovskogo Univesiteta, Moscow, 1990.
11. J. C. Slater, Quantum Theory of Molecules and Solids. Symmetry andEnergy Bonds in Crystals, McGraw-Hill, New York, 1965, vol. 2.
12. W. Van der Lugt and W. Geerstma, Can. J. Phys., 1987, 65, 326.13. V. N. Korchunov, Elektrokhimiya, 1981, 17, 295.14. J. Hildebrand, J. Am. Chem. Soc., 1913, 35, 501.15. R. S. Nigmetova, V.F. Kiselev and L.F. Kozin, Zh. Fiz. Khim., 1982,
56, 2080.16. R. S. Nigmetova, A. K. Kulikovskii, V. F. Kiselev and L. F. Kozin, Zh.
Fiz. Khim., 1986, 60, 1782.
Table 3.5 Diffusion of mercury in solid pure metals.
Metal T (1C) T (K) D0 (cm2 s–1) Q (kJmol–1) Ref.
Ag 0.08 159.4 49Au 600–1000 873–1273 0.116þ 0.13–0.06 156.4� 6.7 50Cu 0.35 184.1 49, 54Pb 200–300 473–673 1.05� 0.24 95.0� 0.84 51Sn[110] 175–232 448–505 30þ 20–12 112.1� 2.1 52Sn[001] 175–232 448–505 7.5þ 6.4–3.5 105.9� 2.5 52Zn8 260–413 533–686 0.056� 0.002 82.4� 0.2 53Zn $ 260–423 533–686 0.073� 0.006 84.4� 0.4 53
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17. O. J. Kleppa, M. Kaplan and C. E. Thalmayer, J. Phys. Chem., 1961,65, 843.
18. J. H. Hildebrand, Viscosity and Diffusivity: a Predictive Treatment,Wiley-Interscience, New York, 1977.
19. C. Guminski, J. Mater. Sci., 1989, 24, 2661.20. D. K. Belachenko, Yavlenia Perenosa v Zhidkikh Metal i Poluprovodihakh,
Atomizdat, Moscow, 1970.21. L. F. Kozin, Physico-Chemishkie Osnovi Amalgamnoi, Metallurgia,
Alma-Ata, 1964.22. A. R. Regel’ and S. I. Patyanin, Atomic Energy, 1963, 14, 114.23. C. Guminski and Z. Galus, Metals in Mercury, Solubility Data Series, ed.
C. Hirayama, Pergamon Press, Oxford, 1986.24. J. B. Edwards, E. E. Hucke and J. J. Martin, J. Electrochem. Soc., 1968,
115, 488.25. A. A. Ravdel and A. S. Moshkevits, Zh. Prikl. Khim., 1971, 44, 178.26. W. T. Foley and M. T. H. Lui, Can. J. Chem., 1964, 42, 2607.27. L. F. Kozin, Amalgam Pyrometallurgy, Nauka, Alma-Ata, 1973.28. L. F. Kozin, Physicochemical Research of Amalgam Methods Used to
Obtain High-Purity Metals: Synopsis of Thesis, Doctoral of ChemicalSciences, Alma-Ata, 1964.
29. L. F. Kozin, R. S. Nigmetova and M. B. Dergacheva, Thermodynamics ofBinary Amalgam Systems, Nauka, Alma-Ata, 1979.
30. W. T. Foley and L. E. Reid, Can. J. Chem., 1963, 41, 1782.31. V. P. Shvedov, A. Z. Frolkov and G. D. Nikitin, Radiokhimii, 1971,
13, 252.32. L. F. Kozin and M. B. Dergacheva, Zh. Fiz. Khim., 1969, 43, 249.33. B. Predel and D. Rothacker, Acta Met., 1967, 15, 135.34. B. Predel and G. Oehme, Z. Metallkd., 1974, 65, 525.35. S. Ziegel, E. Peled and E. Gileadi, Electrochim. Acta, 1979, 24, 513.36. A. W. Castleman Jr and J. J. Conti, Phys. Rev. A, 1970, 2, 1975.37. C. Guminski and Z. Galus, J. Electroanal. Chem., 1977, 83, 139.38. H. Kao and C. G. Chang, Acta Sci. Nat. Univ. Nanking, 1965, 9,
326.39. K. Zh. Sagadeva, A. I. Zebreva and T. L. Badamova, Elektrokhimiya,
1979, 15, 210.40. E. A. Zakharova, G. A. Kataev, L. A. Ignateva and V. E. Morozova, Tr.
Tomsk. Gos. Univ., 1973, 249, 103.41. Z. J. Karpinski and Z. Kublik, J. Electroanal. Chem., 1977, 81, 53.42. P. C. Mangelsdorf Jr, Proc. Met. Soc. Conf., 1961, 7, 429.43. K. Zh. Sagadeva, A. I. Zebreva, R. M. Dzholdasova and B. M. Isaberlina,
Elektrokhimiya, 1977, 13, 1378.44. W. Cohen and H. R. Bruins, Z. Phys. Chem., 1924, 109, 397.45. A. G. Stromberg and E. A. Zakharova, Elektrokhimiya, 1965, 1,
1036.46. W. K. Warburton and D. Turnbull, Thin Solid Films, 1975, 25, 71.
Diffusion of Metals in Mercury 59
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47. W. K. Warburton, Phys. Rev. B, 1973, 7, 1341.48. P. J. Shires, A. L. Hines and T. Okabe, J. Appl. Phys., 1977, 48, 1734.49. D. Lazarus, Solid State Phys., 1960, 10, 71.50. A. J. Mortlock and A. H. Rowe, Philos. Mag., 1965, 11, 1157.51. W. K. Warburton, Phys. Rev. B, 1973, 7, 1330.52. W. K. Warburton, Phys. Rev. B, 1972, 6, 2161.53. A. P. Batra and H. B. Huntington, Phys. Rev., 1967, 154, 569.54. A. Sawatzky and F. E. Jaumot Jr, J. Met., 1957, 9, 1207.
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CHAPTER 4
Purification of Mercury UsingChemical and ElectrochemicalMethods
4.1 Technical Requirements for Mercury
Mercury is obtained by burning mercury concentrates that contain cinnabar at773K. Elementary mercury formed in the process evaporates and thencondenses into dedicated chambers.1 The crude mercury is rich with impuritiesthat come to it in the course of cinnabar smelting, since the cinnabar typicallycontains iron, chromium, silver, gold, copper, zinc, lead, cobalt, nickel,antimony, arsenic, manganese and other substances.2 The amount and natureof the impurities depend on the ore where the mercury concentrate was mined.Cadmium, platinum and tin impurities may also be present. Crude organicsubstances and various gases may be introduced into mercury during thepyrometallurgical processing of cinnabar. The solubility of these substancesand gases depends on the temperature.
According to a Russian national standard, the quality of mercury isdetermined by measurement of the amount of non-volatile residues remainingwhen subliming mercury after filtration through chamois. The sublimation iscarried out in a porcelain crucible, then the residue is baked at 500 1C until itsmass is stable. The amount of primary substance and the non-volatile residueshould meet the requirements indicated in Table 4.1.
No national standards (GOSTs) have been established for high-puritymercury. The Nokitosk Mercury Plant produced high-purity mercury incompliance with the specification of P10-6 grade. In this case, the contentof impurity metals (bismuth, zinc, silver, copper, nickel, iron, gallium,titanium, manganese) is 1�10–7–5�10–8% (by mass). The ExperimentalChemical–Metallurgical Plant Giredmeta also manufactured high-purity
Mercury Handbook: Chemistry, Applications and Environmental Impact
By Leonid F Kozin and Steve Hansen
r L F Kozin and S C Hansen 2013
Published by the Royal Society of Chemistry, www.rsc.org
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mercury of RVCh-1 grade. Impurities in the high-purity mercury (%) were asfollows:
Iron 1�10–6Tin 8�10–7Lead 3�10–6Manganese 3�10–7Nickel 1�10–6Chromium 1�10–6Silver 3�10–7Cobalt 2�10–6
Many methods of treatment for obtaining high-purity mercury are known.These methods combine various technologies based on the use of differentphysical and chemical properties of mercury. The most common are complextechnologies that include chemical and pyrometallurgical processes, distillationand fractionation in a carrier gas flow or in vacuum, electrolysis and zonemelting. Here we review some of these processes and, based on analysis of theresults achieved, select the best combination. The remaining methods arediscussed in detail elsewhere.3
4.2 Chemical Methods for Mercury Treatment
Chemical methods for mercury treatment are widely applied both in labora-tories and in industry.1,4–15 There are a number of chemical methods that canbe separated into dry1,7,9,10,13 and wet1,4–15 methods. The dry methods arebased on oxidation of the impurities and their transformation to oxides, whichare then removed through filtration.7,8,11 Air oxygen, pure oxygen or ozone isused as the oxidant. When using oxygen, the process is run at 423K (150 1C) byblowing compressed air or treated oxygen10 through liquid mercury orcombining this process with mercury distillation in vacuum.16 However,oxidation of impurities in mercury by air oxygen is slow. In a method reportedby Kuzmenkov,10 oxygen from which traces of organic substances had beenremoved was blown at 323K through four quartz vessels containing mercuryand connected in series. This process was run for 24 h and the oxides that wereformed were removed by filtration. However, such methods do not allow forremoval of electrically negative impurities. Generally, the degree of mercurypurification from impurities is low for these methods. To improve the treatment
Table 4.1 Requirements for different grades of mercury.
Mercurygrade
Mercury content,not less than (%)
Non-volatile residuecontent, not less than(%)
P0 99.9992 0.0008P1 99.999 0.001P2 99.990 0.010P3 99.900 0.100
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efficiency, a layer of HNO3 is poured on the top of mercury and air is passedthrough the mercury for 1 week. Subsequently, traces of the acid are washedout and the mercury is dried17 and then distilled several times in an air flow at543K using the procedure described by Hulett and Minchin.18 To acceleratethe oxidation reaction, small droplets of mercury are passed five times througha column (1.5m�5 cm i.d.) filled with HNO3þHg2(NO3)2, then the mercury iswashed, dried and distilled three times in a stream of oxygen.19 According toMoore,20 the column (1.5m�5 cm i.d.) was charged with an 8% solution ofHNO3, whereas Spicer and Banick21 used a 40% solution of HNO3. In thelatter case, air was blown through mercury for several hours to oxidize theimpurities then, in order to remove the oxides, the mercury was filtered, passedthrough a column containing a 40% solution of HNO3, washed to remove theacid, dried and distilled in vacuum.21 The treatment process proceeds faster ifthe air to be used is heated to 423–433K and contains vapors of acids.1,9,10,22
Tin is completely removed by blowing hot air, that has been passed through avessel containing fuming HCl, through mercury for 12 h. Lead is removed bypassing air at 423K through mercury.1,10 However, the process efficiency is lowin this case; further, this method does not allow for removal of impurities thatare electrically positive with respect to mercury. According to Melnikov,1 amajor shortfall of this method is the need for ultrapurification of large amountsof released gases from mercury to reduce mercury losses and protect theenvironment.
Much more productive is the ozone-based dry process, which also has simpleimplementation requirements. Ozone has high oxidative activity; it not onlyoxidizes metal and sulfide impurities, but also decomposes mercury-solubleorganic compounds.21 In this case, treatment is effective for electrically negativeimpurities (zinc, lead) but not so effective for precious metals. Thus, the silvercontent could only be reduced from 1�10–3 to 4�10–4%.1 In real situations,when ozone is used as oxidant of mercury impurities, a weak nitric acid solutionis introduced into the mercury reactor.1
Wet chemical treatment methods include the following sequence ofoperations: (a) removal of mechanical impurities; (b) removal of organiccompounds; (c) removal of metallic impurities; and (d) washing and removal oftraces of moisture.
Mechanical impurities, which normally remain on the surface of mercury, areremoved by filtering through porous barriers (chamois, cheese cloth, layers ofgauze, filter-paper perforated with a thin quartz needle) or a funnel with an in-built capillary tube bent 45–601 off-horizontal.7 The filtration rate may beincreased by applying negative pressure. The implementation of the filtrationprocess was described by Pugachevich.7 To reduce spattering, the filteringoperation may be combined with a process for organic compound removal byfiltering mercury into a concentrated solution of sodium hydroxide orpotassium hydroxide (20–30%)7,8 contained in a column assembly.
The column has the following operating principle. Mercury is run many timesthrough the column containing the alkaline solution. Often, to remove organicimpurities, mercury lying below a layer of the alkaline solution is rapidly stirred
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with a mechanical mixer, shaken or exposed to ultrasound. Following theremoval (saponification) of organic compounds, mercury is washed with distilledwater to remove alkali and then treated with acidic solutions of oxidants, e.g.nitric acid, to remove metallic impurities. Then mercury is vacuum distilled orelectrochemically purified.
The standard potentials of mercury half-reactions, E0, as shown in Chapter5, are as follows:
E0
Hg2þ2=Hg0¼ 0:7973V
E0
Hg2þ =Hg0¼ 0:854V
E0
Hg2þ =Hg2þ2
¼ 0:920V
i.e., they are electropositive. Therefore, mercury ions (Hg2þ2 ,Hg2þ) are strong
complex-forming agents since they create complex compounds with many non-organic and organic ligands (see Chapter 5). Accordingly, E0 of mercury half-reactions depends on the nature of ligands present in a solution. Table 4.2 givesstandard potentials E0 of mercury for different solutions.
Table 4.2 Standard electrode potentials of half-reactions of mercury at 298K(versus NHE).
Half-reaction E0 (V) Ref.
HgþHþþ eÐHgH –2.281 23
HgSþ 2eÐHgþ S2� –0.70 24
HgSþ 2eÐHgþ S2� –0.69 28
HgðCNÞ2�4 þ2eÐHgþ 4CN� –0.370 24,27,28
Hg2ðCNÞ2þ2eÐHgþ 2CN� –0.360 24
HgðSCNÞ2�4 þ2eÐHgþ 4SCN� –0.092 23
Hg2ðSCNÞ2þ2eÐHgþ 2SCN� þ0.22 24Hg2OþH2Oþ 2eÐHgþ 2OH� þ0.123 24–26HgOþH2Oþ 2eÐ2Hgþ 2OH� þ0.098 27Hg2I2þ 2eÐ2Hgþ 2I� –0.0405 24,28
HgI2�4 þ 2eÐHgþ 4I� –0.038 24,28
Hg2Br2þ 2eÐ2Hgþ 2Br� 0.1397 28,26
HgBr2�4 þ 2eÐHgþ 4Br� 0.223 28
HgðOHÞ�3 þ 2eÐHgþ 3OH� 0.231 25Hg2Cl2þ 2eÐ2Hgþ 2Cl� 0.267 24
HgCl2�4 þ 2eÐHgþ 4Cl� 0.380 24
Hg2C2O4þ 2eÐ2Hgþ C2O2�4
0.417 24,26
Hg2CrO4þ 2eÐ2Hgþ CrO2�4
0.540 26
Hg2SO4þ 2eÐ2Hgþ SO2�4
0.6151 24,26
2HgCl2þ 2eÐHg2Cl2þ2Cl� 0.630 24Hg2HPO4þHþþ 2eÐ2HgþH2PO
�4
0.638 25,26
HgFþþ 2eÐHgþ F� 0.602a 23
aOur calculation.
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As can be seen from Table 4.2, the standard electrode potentials of mercuryin the presence of ligands that create strongly complexing compounds withmercury (SCN–, CN–, S2–, Na2S2, Na2Sn, Cl
–, Br–, I– in excessive amounts), andalso in equimolar solutions of halides due to the formation of poorly soluble
mercury salts (Hg2þ2 ), shift the equilibrium toward the electronegative side, with
the half-reaction potentials E0 in strongly complex-forming environments(SCN–, CN–, S2–) changing by as much as 1.07–1.55V. Therefore, in order toremove impurities that are more negative and stand higher in the electrochemicalseries with respect to mercury (Table 4.3), simple electrolytes must be used(HNO3, HClO4þHNO3, H2SO4, CCl3–COOH, dilute HClþHNO3, etc.), the
anions (ligands) of which do not form stable complexes with mercury ions Hg2þ2and Hg2þ. Metallic impurities are removed frommercury via exchange reactions:
z
2Hg2þ2 þMei Hgð ÞxÐMezþi þ xþ 2ð ÞHg ð4:1Þ
z
2Hg2þ þMei Hgð Þx$Mezþi þ xþ 1ð ÞHg ð4:2Þ
and include metals and metalloids more negative than mercury (As, Cu, Bi, Sb,Pb, Sn, Ni, Co, Tl, In, Cd, Fe, Cr, Ga, Zn, Mn, Al) and other more electro-negative impurities.
Comparison of the data in Tables 4.2 and 4.3 shows that in complex-formingmedia and also in chloride, bromide and iodide solutions, the difference inpotentials
DE¼EHg2þi=Hg0 � EMezþþMe0 ði¼ 1; 2Þ
decreases or even becomes negative for some electrolytes. The nature of theelectrolytes affects the electrode potentials of mercury and metals in differentways (compare Tables 4.2 and 4.3). An example is the way in which thepotentials of gold change compared with mercury in cyanide solutions (CN–)and solutions formed by simple (H2O) electrolytes (Table 4.4).
It can be seen that DEMe2þ
2=Me0
and DEMezþ =Me0
for mercury and gold are
1.14 and 2.31V, respectively; whereas gold, more positive in the solutions ofsimple electrolytes compared with mercury, acquires a negative potential incyanide electrolytes. Chapter 5 demonstrates that the introduction of ligandsinto the solution of the system Hgliquid
0–Hg2X2–HgX2–HY–H2O (where X is ahalide and Y is an anion ligand) results in convergence of standard potentialsand a shift of half-reaction potentials (see Tables 4.2, 4.3 and 5.4) towards thenegative side. At the same time, Kreprop values decrease and Kdisprop values (asKdisprop¼ 1 =Kreprop) increase and conversion of potentials takes place:
E0
Hg2þ =Hg2þ2
oE0Hg2þ
2=Hg
4E0Hg2þ =Hg
and lower valence ions of mercury become unstable in the systemHgliquid
0–Hg2X2–HgX2–HY–H2O.
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Table 4.3 Standard electrode potentials of half-reactions of metals at 298K(versus NHE).23–25,27–29
Half-reaction E0 (V) Half-reaction E0 (V)
Ti2þþ2e¼Ti –1.750 CuðCNÞ�2 þe¼Cuþ 2CN� –0.430
Be2þþ2e¼Be –1.700 Cd2þþ2e¼Cd –0.404
Al3þþ3e¼Al –1.670 PdðCNÞ2�4 þ2e¼Pdþ 4Cn� –0.400
Zr4þþ4e¼Zr –1.530 PbI2þ2e¼Pbþ 2I� –0.365
ZnSþ 2e¼Znþ S2� –1.440 Cu2OþH2Oþ 2e¼ 2CuþOH� –0.361
ZnðCNÞ2�4 þ2e¼Znþ 4CN� –1.260 In3þþ3e¼ In –0.340
ZnðOHÞ2þ2e¼Znþ 2OH� –1.245 Tlþþe¼Tl –0.338
CdSþ 2e¼Znþ S2� –1.230 PtSþ 2Hþþ2e¼PtþH2S –0.300
V2þþ2e¼V –1.180 AgðCNÞ�2 þe¼Agþ 2CN� –0.300
Nb3þþ3e¼Nb –1.100 CuCNSþ e¼Cuþ CNS� –0.270
Mn2þþ2e¼Mn –1.050 PbCl2þ2e¼Pbþ 2Cl� –0.268
Tl2Sþ 2e¼ 2Tlþ S2� –1.040 CuSþ 2Hþþ2e¼CuþH2S –0.259
FeSðaÞ þ 2e¼Feþ S2� –1.010 Sb2O3þ6Hþþ6e¼ 2Sbþ 3H2O –0.255
InðOHÞ3þ3e¼ Inþ 3OH� –1.000 Ni2þþ2e¼Ni –0.250
PbSþ 2e¼Pbþ S2� –0.980 SnF2�6 þ4e¼ Snþ 6F� –0.250
SnSþ 2e¼ Snþ S2� –0.940 CuðOHÞ2þ2e¼Cuþ 2OH� –0.224
CdðCNÞ2�4 þ2e¼Cdþ 4CN� –0.900 CuIþ e¼Cuþ I� –0.187
RhðCNÞ2�6 þe¼RhðCNÞ2�3 þCN� –0.900 AgIþ e¼Agþ I� –0.151
Cr2þþ2e¼Cr –0.900 Sn2þ þ 2e¼ Sn –0.140
NiSðaÞ þ 2e¼Niþ S2� –0.860 Pb2þþ2e¼Pb –0.126
SbS�2 þ3e¼ Sbþ 2S2� –0.850 OsO2�2H2Oþ 4e¼Osþ 4OH� –0.120
PtSþ 2e¼Ptþ S2� –0.830 WO3þ6Hþþ6e¼Wþ 3H2O –0.090
NiðCNÞ2�4 þ2e¼NiðCNÞ2�3 þCN� –0.820 O2þH2Oþ 2e¼HO�2 þOH� –0.076
CdðOHÞ2þ2e¼Cdþ 2OH� –0.810 AgCNþ e¼Agþ CN� –0.040
Zn2þþ2e¼Zn –0.762 RuO2þ2H2Oþ 4e¼Ruþ 4OH� –0.040
TlIþ e¼Tlþ I� –0.760 CuI2þe¼Cuþ 2I� 0.0
CuSþ 2e¼Cuþ S2� –0.760 HOsO�5 þ4H2Oþ 8e¼Osþ 9OH� 0.000
CrClþ2 þ3e¼Crþ 2Cl� –0.740 CuBrþ e¼Cuþ Br� 0.033
CoðOHÞ2þ2e¼Coþ 2OH� –0.730 Rh2O3þ3H2Oþ 6e¼ 2Rhþ 6OH� 0.040
Cr3þþ3e¼Cr –0.710 CuBr�2 þe¼Cuþ 2Br� 0.050
HgSþ 2e¼Hgþ S2� –0.700 PdðONÞ2þ2e¼Pdþ 2OH� 0.070
TlBrþ e¼Tlþ Br� –0.658 AgBrþ e¼Agþ Br� 0.073AuðCNÞ�2 þe¼Auþ 2CN� –0.600 PtðCNÞ2�4 þ2e¼Ptþ 4CN� 0.090
ReO�4 þ4H2Oþ 7e¼Reþ 8OH� –0.584 HgOþH2O¼Hgþ 2OH� 0.098PbOþH2Oþ 2e¼Pbþ 2OH� –0.578 PdðOHÞ2þ2e¼Pdþ 2OH� 0.100PbSþH2Oþ 2e¼PbþOH�þSH� –0.560 Ir2O3þ3H2Oþ 6e¼ 2Irþ 6OH� 0.100TlClþ e¼Tlþ Cl� –0.557 CuClþ e¼Cuþ Cl� 0.124
Cu2Sþ 2e¼ 2Cuþ S2� –0.540 Hg2Br2þ2e¼ 2Hgþ 2Br� 0.139
Ga3þþ3e¼Ga –0.520 PdðSCNÞ2�4 þ2e¼Pdþ 4SCN� 0.140
BiOOHþH2Oþ 3e¼Biþ 3OH� –0.460 ReO4þ8Hþþ7e¼Reþ 4H2O 0.150
Fe2þþ2e¼Fe –0.441 Sb2O3þ6Hþþe¼ 2Sbþ 3H2O 0.152
BiCl�4 þ3e¼Biþ 4Cl� 0.160 RuCl2�5 þ3e¼Ruþ 5Cl� 0.600
BiOClþ 2Hþþ3e¼BiþH2Oþ Cl� 0.160 RuO2þ4Hþ ¼Ruþ 2H2O 0.680
Cu2þþe¼Cuþ 0.167 IrCl3�6 þ3e¼ Irþ 6Cl� 0.720
PdI2�4 þ2e¼Pdþ 4I� 0.180 PtCl2�4 þ2e¼Ptþ 4Cl� 0.730
CuCl�2 þe¼Cuþ 2Cl� 0.190 Fe3þþe¼Fe2þ 0.771
PtðOHÞ2þ2e¼Ptþ 2OH� 0.200 Hg2þ2 þ2e¼ 2Hg 0.789
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This is why chemical treatment methods commonly rely on solutions of nitricacid, nitrates and perchlorates of mercury(I) and -(II). Exchange reactions (4.1)and (4.2) take place upon contact between mercury-containing impurities and amercury salt solution. Equilibrium exchange reactions (4.1) between ions of
mercury Hg2þ2 and more electronegative impurities may be described by the
equation
Kp¼aMezþa
xþ2Hg
aMeðHgÞaz = 2
Hg2þ2
ð4:3Þ
Equilibrium in the system MeðHgÞ =Hg2þ2 is reached if there are equal
potentials EHg2þ =Hg¼EMezþ =Me0
¼E:
EHg2þ2=Hg0 ¼ E0
Hg2þ2=Hg0þ RT
2Fln
CHg2þ2gHg2þ
2
CHg0gHg0
" #ð4:4Þ
Table 4.4 Change in potentials (V) of gold and mercury in different solutions.
Potential H2O CN– DE (V)
EHg2þ
2=Hg0
0.789 –0.360 1.14
EAuþ =Au0
1.70 –0.61 2.31
EHg2þ =Hg0
0.854 –0.370 1.22
EAu3þ =Au0
1.50 –0.810 2.31
Table 4.3 (Continued)
Half-reaction E0 (V) Half-reaction E0 (V)
HgBr2�4 þ2e¼Hgþ 4Br� 0.210 Agþþe¼Ag 0.799
AgClþ e¼Agþ Cl� 0.222 Rh3þþ3e¼Rh 0.800
Hg2Cl2þ2e¼ 2Hgþ 2Cl� 0.244 OsO4þ8Hþþ8e¼Osþ 4H2O 0.840
Ru3þþe¼Ru2þ 0.249 IrCl3�6 þ3e¼ Irþ 6Cl� 0.860
Hg2Cl2þ2e¼ 2Hgþ 2Cl� 0.267 AuBr�4 þ3e¼Auþ 4Br� 0.870
Cu2þþ2e¼Cu 0.345 2Hg2þþ2e¼Hg2þ2 0.920
HgCl2�4 þ2e¼Hgþ 4Cl� 0.380 PdCl2�6 þ4e¼Pdþ 6Cl� 0.920
PtI2�4 þ2e¼Ptþ 4I� 0.400 AuBr�4 þe¼Auþ 2Br� 0.960
PtI2�6 þ4e¼Ptþ 6I� 0.400 Pd2þþ2e¼Pd 0.987
RhCl3�6 þ3e¼Rhþ 6Cl� 0.440 AuCl�4 þ3e¼Auþ 4Cl� 1.000
AuIþ e¼Auþ I� 0.500 RuO4þ8Hþþ8e¼Ruþ 4H2O 1.040
Cuþþe¼Cu 0.522 RhO2�4 þ8H
þþ6e¼Rhþ 4H2O 1.100
Hg2CrO4þ2e¼ 2Hgþ CrO2�4
0.540 AuCl�2 þe¼Auþ 2Cl� 1.130
Te4þþ4e¼Te 0.568 Pt2þþ2e¼Pt 1.200
PtBr2þ4 þ2e¼Ptþ 4Br� 0.580 RhCl2�6 þe¼RhCl3�6 1.200
PdCl2�4 þ2e¼Pdþ 4Cl� 0.590 Au3þþ2e¼Auþ 1.290
OsCl3�6 þ3e¼Osþ 6Cl� 0.600 Au3þþ3e¼Au 1.500
PdBr�4 þ2e¼Pdþ 4Br� 0.600 Auþþe¼Au 1.700
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EHg2þ2=Hg0 ¼ E0
Hg2þ2=Hg0þ RT
2Fln
CMezþgMezþ
CHg0gHg0
" #ð4:5Þ
where gi are activity coefficients.By subtracting eqn (4.5) from eqn (4.4) and considering that½CHg2þ
2gHg2þ
2CMe0gMe=CMezþgMezþCHg0CHg0 � ¼Kp, one finds the equilibrium
constant to be4,30
lnKp¼2� zð ÞFE þ zFE0
Mezþ =Me0� 2FE0
Hg2þ2=Hg0
RTþ ln
gHg2þ2gMe0
gMezþgHg0
!ð4:6Þ
At gHg2þ2¼ gMezþ ¼ 1, gMe0 ¼ gHg0 and z¼ 2, eqn (4.6) is reduced to4,30
lnKp¼2F
RTE0
Mezþ =Me0� E0
Hg2þ2=Hg
� �ð4:7Þ
Equation (4.7) shows that larger potential differences have a greater equi-librium constant, Kp, of the exchange reaction. For exchange reaction (4.2), we
obtain equations appearing similar to eqns (4.6) and (4.7) if E0Hg2þ
2=Hg
is
replaced with E0Hg2þ =Hg
and gHg2þ2
is replaced with gHg2þ .
The principles of exchange reactions in systems with liquid mercury andamalgam electrodes have been set out.4,6,31–33 Exchange reactions described byeqns (4.1) and (4.2) occur at a very high rate. In reactions (4.1) and (4.2), theexchange process normally obeys first-order kinetics:
lnC
C0¼ kt ð4:8Þ
where k is the rate constant and t is time and depends on the nature of themetals and the electrolyte.
Kinetic rates of exchange reactions of Hg2þ2 ions in a nitrate solution [0.5 M
Hg2(NO3)2þ 2MHNO3] with amalgams of copper, lead and cadmiumcontaining 0.1 at.% metal are given in ref. 3. The exchange rate increases in thesequence Cu-Pb-Cd (kCu¼ 1.1�10–4, kPb¼ 2.1�10–4, kCd¼ 4.0�10–4 s–1).The same sequence is characterized by increasing solubility of the metals inmercury (in the experiments copper amalgam was heterogeneous) andincreasing atomic and ionic radii. According to Kozin,4 the exchange reactionrate constant depends on the diffusion coefficient (D), Hg(Mei)/solution phaseboundary (S), diffusion layer thickness (d) and reaction system volume (n):
k¼ DS
dnð4:9Þ
Therefore, increases in D and S and decreases in d and n yield higher exchangereaction rates. To reduce d, one needs to keep the solution in active motion nearthe surface of mercury.4 The phase exchange rate depends on thehydrodynamic conditions of the solution’s motion relative to mercury.
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It will be observed that if crude mercury containing a range of metalimpurities is used, exchange reactions take place not only between ions ofmercury and the impurities, but also between electropositive impuritiescontained in the solution and electronegative impurities contained in mercuryaccording to the reaction
Mezþ1 þMe2ðHgÞÐMezþ2 þMe1ðHgÞ ð4:10Þ
In this case, the exchange rate also depends on the experimental conditions.The rate of exchange reaction in log(C/C0) versus t and Z versus t coordinates asa function of the stirring rate of cadmium sulfate solution and zinc amalgamhas been reported.34 The exchange rate depends strongly on the stirring rate.The curves depicting the isolation of cadmium from the solution as a functionof contact time between zinc amalgam and the solution (Z versus t) suggest alogarithmic relationship. Indeed, the log(C/C0) versus t relationship is linear,which points to diffusion control of the phase exchange.
The relationship between the concentration of cadmium ions and the rateof exchange ratios has also been reported.34 The exchange reaction rateconstant does not depend on the concentration of cadmium ions in the elec-trolyte. The data indicate that higher temperatures cause higher exchangereaction rates. At 283K, 99.9% of cadmium ions take as long as 385 min toengage in an exchange reaction with zinc amalgam, whereas at 348K the sameprocess takes only 48 min. The phase exchange rate constants (s–1) are asfollows:
283K 4.6�10–5298K 9.1�10–51323K 1.6�10–41348K 2.9�10–4
The temperature dependence of the effective constants of exchange rates isused to calculate the activation energies of exchange reactions. Experimentallydetermined exchange reaction rate constants as functions of the reciprocal oftemperature can easily fit a straight line. The expected activation energy of theexchange reaction between cadmium ions and zinc amalgam is 23.0kJmol–1 andsuggests that the exchange process is restricted by concentration limitations.
Kozin et al.34 considered the exchange reaction mechanism based on theCd21/Zn(Hg)x system:
Cd2þ þ ZnðHgÞÐCdðHgÞ þ Zn2þ ð4:11Þ
The polarization curves show the discharge–ionization of zinc and cadmium atamalgam electrodes (5.0 at.% amalgam) in the sulfuric acid electrolytesanalyzed. The same curves also show that ionization of both zinc fromamalgam and cadmium takes place with some polarization. The discharge ofcadmium ions at an amalgam electrode occurs with considerable polarization,probably because in sulfuric acid solutions cadmium is bound into a negativelycharged anionic complex.35 The cadmium ion concentration in the solution
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increases as the polarization in the course of discharge decreases. According toSmirnova et al.,36, the zero discharge potential for 5.6 at.% zinc and 5.6 at.%cadmium amalgams is 0.45 and 0.42 V, respectively.36,37 Therefore, theCd21–Zn(Hg) exchange reaction takes place on the negatively charged surfaceof zinc amalgam. The equilibrium potential of 5.0 at.% zinc amalgam is 0.805in the presence of 1 g L–1 Zn21 and 0.740 V at 100 g L–1 Zn21.
The exchange reaction between ions of cadmium (Cd21) and atoms of zincpresent in the amalgam produces Zn21, which are adsorbed on the negativelycharged surface of zinc amalgam, making it difficult for Cd21 ions to reach theamalgam surface. By this reaction, Zn21 ions produced in the course of theexchange reaction push Cd21 ions back from the near-electrode layer. Theexchange reaction then becomes inhibited. Apparently, the rate of the anodereaction:
ZnðHgÞÐZn2þ þHgþ 2e ð4:12Þ
may be much greater than the rate of cathode reaction:
Cd2þ þHgþ 2eÐCdðHgÞ ð4:13Þ
The cathode reaction is the limiting factor of the exchange reaction (4.11). Itis expected that a flow of zinc ions generated on the surface of the amalgam andbearing the same charges as cadmium ions will prevent the cadmium ions fromreaching the surface of the amalgam due to an emerging electrostatic repulsion.Suppose that if an additional electrode is submerged and positioned in contactwith zinc amalgam and the solution, the ionization of zinc atoms from theamalgam and the cathodic discharge of cadmium ions may be separated bysome space. The reaction rate should now increase.
The increase of the exchange reaction rate constant for Cd21 ions achievedvia spatial separation of the processes taking place at the amalgam–solutionphase boundary with the help of an additional electrode, on which cadmiumsettles the most, occurs because the arrangement avoids the limiting phase ofCd21 ion reduction at the amalgam electrode. Experiments have shown thatonly 10% of Cd21 ions penetrate the layer of Zn21 ions on their way to theamalgam–solution phase boundary.
The effect of electrostatic repulsion of Bi31 ions by the positively chargedouter double layer of the amalgam has been described.38 In this case, ifelectrons were diverted with the help of an additional electrode, the exchangereaction rate constant increased 4.2-fold. It has been demonstrated that ifelectrons are diverted during the reduction of the bismuth ions, only 8–10% ofbismuth enters the zinc amalgam.
The relatively low exchange rates in the Hg2þ2 =Hg system are also apparently
due to the electrostatic repulsion effect. The zero charge potential of mercury is0.21V (see Chapter 6); consequently, the mercury surface is positively charged,which causes a mutual repulsion of the like positive charges of mercury from
the surface and from the Hg2þ2 ions and ultimately reduces mass transfer in the
system.
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Another reaction takes place at high nitric acid concentration along with theexchange reaction, in which HNO3 reacts with mercury and the impurities:
6Hgþ 8HNO3 ! 3Hg2ðNO3Þ2 þ 2NOþ 4H2O ð4:14Þ
In concentrated HNO3 solutions the following reaction takes place:
3Hgþ 8HNO3 ! 3HgðNO3Þ2 þ 2NOþ 4H2O ð4:15Þ
The resulting mercury(II) ions react with mercury according to
HgðNO3Þ2 þHg! Hg2ðNO3Þ2 ð4:16Þ
Impurities contained in the mercury react as follows:
HgðNO3Þ2 þMeðHgÞx !MeðNO3Þ2 þ ðxþ 1ÞHg ð4:17Þ
The nitrate solution-based treatment process is lengthy39,40 and, given astandard implementation setup, requires ceaseless attention and causes sizablematerial losses.26
To upgrade productivity, reduce mercury losses and improve laborconditions, semiautomatic41 and automatic42,43 chemical treatment instal-lations were designed. Mercury is purified42 after many cycles of operation,using two processes: air blasting and chemical treatment. Air is suppliedthrough a porous glass filter to improve treatment quality and avoid uninten-tional impurities. Stable column operation is achieved by increasing water flow.To initiate the purification process, the column is loaded with 0.1 L of mercuryand 0.75L of process liquid. Mercury is added to the column in 0.075Lportions from time to time during column operation. Mercury circulates ataround 0.120Lmin–1 under normal operating conditions and completes B100cycles in 1 h. Based on this design, Artamonov42 created a three-stage mercurypurification column. The first column used a 20% solution of sodiumhydroxide, the second a 5% solution of nitric acid and the third was filled withdistilled water. Each portion of prefiltered mercury passes through all the threecolumns in succession. If all columns are activated, the installation produces0.075L h–1 of high-purity mercury.
Krolikiewicz et al.40 proposed a high-performance chemical treatmentinstallation. The installation consists of (a) an accumulation container forcrude mercury equipped with a drain pipe and an overflow outlet in the upperpart to drain excess water in case of overfilling, (b) three identical columnsconnected in series and (c) a pure mercury receptacle. The columns arecylinders with hemispherical bottoms. Each column has a pipe built into italong the centerline; the pipe runs full length and narrows at the top. Inside theshell, a U-shaped siphon drain pipe enters from the bottom, reaching aroundhalf of the column height. The space between the pipe and the walls is filled withglass balls. The container is topped with a dish-shaped cover with holes toaccept mercury.
Another high-performance mercury treatment method, based on the useof nitric acid solutions with Hg2(NO3)2 in a column equipped with a
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graphite–glass nozzle, has been suggested.43 The process allows continuouspurification of mercury flows in solutions of constant acidity and mercury(I)ion concentration. As mercury becomes free of impurities, it loses its capacityto form a uniform liquid layer and gradually turns into a mass consisting of1–1.5mm balls (‘fish eggs’). These balls merge only if stirring ceases andmercury is allowed to settle out for 10–15min. Mercury can then be washedwith doubly distilled water to remove electrolyte and dried by filtration througha filter-paper perforated with thin quartz needles.
The method of Klinsky et al.44 may also be used with some modifications.They proposed a mercury treatment method to remove zinc, cadmium, copper,bismuth, lead and tin in which mercury is exposed to mercurous compoundsbound by an ion-exchange resin (KU-1, KU-2, KRS, KB-4 and various typesof sulfocationites) in the form of monovalent cations of mercury(I) using resingrain sizes of 0.02–0.60mm. Mercury is pumped through a layer of ion-exchange resin at the rate of 185–2700 kgHgm–2 h–1. The method yieldsexcellent results. With original zinc, cadmium, copper, lead, bismuth and tinimpurities at 0.5mol L–1 (in separate tests), after mercury had been pumpedthrough a layer of ion-exchange resin at the rate of n¼ 185–810 kg Hg m–2 h–1,the impurities had decreased to the following levels (mol L–1):
Zn 5�10–7Cd 1�10–6Cu 2�10–9Bi 5�10–6Pb 8�10–6Sn 8�10–6
For mercury containing zinc, cadmium and copper at 0.17, 0.15 and 0.18molL–1
at n¼ 2700 kg Hg m–2 h–1, the post-treatment impurity contents (mol L–1) were
Zn 5 �10–7Cd 1�10–6Cu 2�10–8
The treatment efficiency depended on the mercury throughput rate. Thus,for mercury containing 0.33mol L–1 of lead, 0.33mol L–1 of bismuth and0.34mol L–1 of tin, the following post-treatment concentrations were obtained,depending on throughput rate: n¼ 46–2700 kgHgm–2 h–1 gave a maximum of10–6mol L–1, n¼ 3000 a maximum of 10–5 mol L–1 and n¼ 3500 a maximumof 10–2mol L–1. This shows that the throughput rate should not exceed2700mol L–1. There is also evidence that the treatment efficiency depends onthe grain size of the ion-exchange resin. Impurity analyses found a maximum of10–6mol L–1 at a grain size of 0.01–0.60mm, 10–5mol L–1 at 0.650mm and10–2mol L–1 at 0.750mm.44 Data presented by Klinsky et al.44 suggest that theimpurity separation coefficient
x¼P
MeininitialHgPMeintreatedHg
ð4:18Þ
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is between 3.4�105 and 1.0�107. This method is much more efficient than otherknown chemical methods for mercury treatment. However, this method, aswith all other chemical methods, has the problem that mercury does not lose itsimpurities of precious metals – silver, gold, rhodium, iridium, platinum – andalso electronegative metals bound into intermetallic phases.4,5,45,46
Horizontal and vertical magnetohydrodynamic (MHD) pumps4,5,12,38 areused in industrial applications for the chemical treatment of technical mercury.With standard chemical methods, if crude mercury arrives with an array ofimpurities, frequent replacement of spent solutions is necessary andconsiderable losses of mercury are common. Kozin and Ivanchenko38 createdhigh-performance fully automatic industrial plants capable of producing0.2–1.0 t h–1 of mercury containing 99.99–99.9995% of base metal. Theimpurity concentration was reduced from 0.05% wt% (500 ppm) in the originalmercury down to (1–2)�10–3 wt% after treatment. Mercury losses were verysmall, typically (1–3)�10–2 wt%.
Ordinary chemical treatment methods involve losses between 2 and 5 wt%.Such high loss figures are due to the high oxidation capacity of nitric acid withrespect to metallic mercury and to mercury engaging in soluble solutions ofHg2(NO3)2 and Hg(NO3)2. Therefore, sizable amounts of mercury join metalimpurities as part of the solution and often mercury still contains impuritiesthat cannot be completely removed.39,40
Some of the disadvantages mentioned above can be partially overcome by amethod for mercury purification based on H2SO4þKMnO4 solutions,
47, whichsuccessfully removes the following amount (wt%):
Cd 3In 2Tl 2Pb 1Sn 0.5Zn 1.0Cu 0.003Fe 0.003
The treatment process consists of three phases. In Phase 1, equal amounts ofa 9 N solution of H2SO4 and a saturated aqueous solution of KMnO4 areshaken with mercury until the solution is completely colorless. Then newportions of the solution are added while shaking until balls appear on themercury surface. Subsequently, mercury is washed with water to removeimpurities. In Phase 2, the ‘last traces of impurities’ are removed. To do that,mercury is treated with a 2.0 N solution of H2SO4þ a 0.1 N solution of KMnO4
while shaking until there is a large mass of small mercury balls. Once again,mercury is washed with water and shaken with 2 N H2SO4 until there is acomplete mass of mercury balls (Phase 3). Finally, mercury is washed withwater and 2 N H2SO4 yet again until the balls (‘fish eggs’) disappear.
If mercury containing impurities is shaken with a concentrated solution ofiron(III) tetraoxosulfate(IV) in H2SO4 or a mixture of this solution with
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KMnO4, the impurity removal rates increase considerably. The rapid impurityremoval rate is due to catalytic acceleration of KMnO4 reduction as it interactswith FeSO4 – the product of chemical reaction between Fe2(SO4)3 and mercuryimpurities. At the same time, iron(II) sulfate is converted into iron(III) sulfate,which reacts rapidly with the impurities contained in the mercury. With thehelp of a 1N solution of Fe2(SO4)3 in a 2N solution of H2SO4, it took 10 s ofshaking to remove 1 g of lead from 200 g of mercury and 30 s to remove 7 gof zinc.47 With the help of a concentrated solution of KMnO4 in a 6N solutionof H2SO4þ 20 cm3 of a 0.1N solution of Fe2(SO4)3, Russell and Evans47
managed to remove 14 g (total) of Zn, Cd, Sn, Pb solder and Bi from 480 gof mercury without losing any material. A dedicated experiment demonstratedthat the order in which metals are removed from mercury by oxidantscontained in the solutions is different from their position in the standardpotential series only for Cr, Mn, Fe, Co and Ni (atomic numbers 24–28).47,48
The authors explained such behavior by a manifestation of passivity.We have modified the method of Russell and Evans.47 The treatment quality
was controlled using potentiometry. If the measurable potential of mercury in a1M solution was in the range 0.600–0.610V (versus NHE) and was constantwith time, we assumed that metal impurities more electronegative with respectto mercury were completely removed. If the mercury potential tended tomigrate with time towards the negative side, that would indicate that moreelectronegative impurities were bound into intermetallic phases. The inter-metallic phases dissociate and remove the dissolved portion of electronegativeimpurities (see Chapter 2).4,5 The high effectiveness of sulfuric acid solution-based treatment methods is due to the electrochemical properties of theHg2SO4/Hg system. This system demonstrates a positive potential and Hg2SO4
is poorly soluble in water and water-based solutions. Therefore, when oxidantsare introduced into a sulfuric acid solution, they are used only to oxidize theimpurities, since, after the impurities have been removed, the surface of themercury is passivated with a very thin film. The thin film causes mercury tobreak into small balls and turn into ‘fish eggs’ if stirring is applied. This is whythe Hg2SO4/Hg mercury treatment system is easy to automate.
Krolikiewicz et al.40 suggested their own implementation of the chemicalmethod. Crude (contaminated) mercury is purified by passing it through acascade of columns. After passing through a layer of deionized water,contaminated mercury enters the first column. Prior to initiation of thetreatment system, the columns are filled with pure mercury. The method isnoteworthy because mercury is treated with an oxalic acid solution containing1% tartaric (citric) acid, 0.5% progalite and 1% (30%) H2O2.
48 The basis of themethod relies on crude mercury being subjected to rapid mixing with an oxalicacid solution containing additives (o¼ 100 rpm) at 263–353K. In the course oftreatment, a circulation pump continuously forces the solution through a layerof mercury. The method produces mercury containing 99.9% of base metalby mass.
Kobza and Grudina22 developed a method to decontaminate mercury ofgreases, lubricants and mineral oils. A container is loaded with treated mercury
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and a 2–5% aqueous solution of sodium chloride. An Hg:electrolyte volumeratio of about 1:2 is used. AC current is supplied to mutually isolated electrodesintroduced into the electrolyte and mercury. Some time later, the unit isde-energized, electrolyte is replaced and the cycle is repeated. It takes 3–5replacements of electrolyte or the use of a flowing electrolyte to finally obtainhigh-purity mercury.22
4.3 Single-stage Electrochemical Methods for Obtaining
High-purity Mercury
Electrolytic purification of mercury uses the principles of anodic dissolutionand single- or multistage reprecipitation on mercury cathodes. The principle ofstaged anodic dissolution of impurities5 may also be employed. In the case ofanodic dissolution of mercury, the solution acquires more electronegativeimpurity metals, while mercury retains the more electropositive metals – silver,gold, rhodium – and also the more electronegative metals bound into inter-metallic phases.5,45,46 The anodic dissolution process is normally initiated at acurrent density of 0.2Adm–2 in electrolyte containing a 2% solution of nitricacid or a mixture of 5% solutions of nitric and sulfuric acids. The electrolyticprocess removes bismuth, antimony, arsenic, iron, tin and lead, although notcompletely enough. Anodic dissolution methods yield the same degree ofpurification as the chemical methods.
Technologically, the single-stage electrolysis-based deep treatment methodconsists of dissolution of the original crude mercury, which contains moreelectronegative (Mej) and electropositive (Mei) metallic impurities (HgMeiMej),in the electrolyzer’s anode space:
HgMeiMejÐHgx�1Mei þHgzþ þMemþj þ zþmð Þe ð4:19Þ
and cathodic deposition of mercury ions Hgz1 at the mercury cathode in theelectrolyzer’s cathode space:
Hgx þHgzþ þ zeÐHgxþ1 ð4:20Þ
where z¼ 1 or 2 depending on the nature of the electrolyte. For complexes with
composition HgXðz�nÞz (X¼Cl–, Br–, CN–, SCN–, etc.), z¼ 2. In simple elec-
trolyte solutions (X¼ClO4–, NO3
–, ClO3–), z¼ 1.
A basic outline of the processes occurring during single-stage electrolyticpurification of mercury was given by Kozin.3 When crude mercury (1) is addedto the anode space, the anode receives more electropositive and more electro-negative impurity metals. The single-stage mercury purification process is basedon mass transfer of mercury by the action of electric current with its ionizationat the mercury anode together with electronegative impurities, accordingequation (4.19), and electrodeposition of mercury ions on the cathode,according to equation (4.20). In theory, more positive impurities should remainin the mercury anode and stay away from the electrode process. However, thebehavior of electropositive impurities depends on the experimental conditions.
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Kozin3 also showed concurrent (including ‘parasitic’) processes 3–9, explainedas follows. Processes 3 and 4 are related to the reduction of the ions of thetreated metal–mercury (Hg2
21, Hg21, HgX2, HgX42–, etc.) by electronegative
metal impurities (Mei0) contained in crude mercury. At the same time, more
electronegative impurities migrate into the electrolyte solution according to eqn(4.1) or (4.2). Processes 5 and 6 are due to migration of cathodic mercury, Hgx,into the solution and electropositive impurities, Mej, into cathodic mercury as aconsequence of phase exchange reactions:
Hgx þMezþjaqÐHgzþ þ Mej� �
Hgx ð4:21Þ
The principles of exchange reactions are covered in the literature.4,5,7,49 Process7 consists of electrochemical dissolution of electropositive metals contained inthe mercury anode (crude mercury):
Mej� �
HgxÐMezþj þHgx þ ze ð4:22Þ
Process 8 is due to the interaction between more electrically positive tracemetals in the electrolyte with the mercury being purified in the course ofexchange reaction:
Mezþj þHgxÐ Mej� �
Hgx�1 þHgzþ ð4:23Þ
The results of a single-stage purification of mercury have been presented.50,51
Usually, purification is performed in electrolyzers with separate anode andcathode spaces in an electrolyte composed of 235 gL–1 perchloric acid and200 gL–1 mercury oxide.50 During electrolysis, the mercury(II) perchlorate isreduced to univalent mercury. Studies of the behavior of trace metals such aszinc, cadmium, tin, bismuth, copper, silver and gold introduced in the mercuryto be purified in amounts of 0.02–0.1% during electrolysis have shown that in anumber of experiments copper and gold were found in some batches of purifiedmercury.
The perchloric acid electrolyte was prepared1 by dissolving 20 cm3 of a 75%solution of HClO4 in 80 cm3 of water and then dissolving 20 g of mercury oxidein the solution obtained. Mercury(II) perchlorate is formed during electrolysisand by contact of metallic mercury is reduced to Hg2(ClO4)2. Along withreduction of mercury(II) ions to mercury(I) ions in the course of electrolysis,reduction of mercury(I) to metallic mercury takes place.
Feryanchich51 carried out the electrolytic purification of mercury in asolution of nitric acid (1:2) at an initial current density of 0.2Adm–2. As theelectrolyte was being saturated with mercury ions, the anode current densityincreased to 1.5Adm–2. During the electrolysis, the content of impurities in therefined mercury decreased from 0.12 to 0.007 wt%. According to Lorenz,51, theanode residue mainly contained iron.
For mercury treatment under laboratory conditions,38 a thick-walledcrystallizer of diameter 20–25 cm was suggested. A 5% solution of HNO3 servesas the electrolyte. Between 3 and 4 kg of raw mercury is loaded into thecrystallizer and covered with the solution. Current is fed to a mercury cathode
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and anode through platinum wires soldered into tubes. The electrolysis takesplace with agitation of anode mercury and the electrolyte with an agitator. Thevoltage applied to the electrodes is 5–6V and the electrolysis current is 5–8A.Metallic impurities pass from the purified mercury to the solution and, inaccordance with the separation factors, are formed on the cathode.
Depending on the degree of mercury contamination, the impurities turn theelectrolyte dark in 5–10 min. The electrolyte is then drained using a siphon anda fresh portion of a 5% solution of HNO3 is loaded. The electrolyte will bechanged 3–8 times until coloration stops.38 This suggests that electrolytictreatment of raw mercury is ineffective and that chemical treatment should beperformed first. The use of a stationary mercury cathode also reduces theefficiency of single-stage electrolytic purification.
Lorenz52 reported a design of an electrolyzer where efficient agitation of theanode and cathode is ensured. A current of 10A and voltage of 12V is applied.Impurities (Zn, Co, Pb, Sn, Sb, Cu, Ag) are removed through anodicdissolution of mercury at a current density of 50–60Adm–2. Heat is dissipatedusing air or water cooling. Noble metals – Au and Pt – remain in the mercury.To obtain high-purity mercury (99.9999%) after anodic treatment, mercury issubjected to vacuum distillation.52 Electrolyzers of this design can also be usedfor a single-stage electrolytic treatment.
Analysis of the literature on mercury purification5,7–10,50,52 shows that elec-trolytes are generally composed of nitric acid solutions and have the disad-vantage of being unstable over time. From experience, the single-stage methodcannot achieve ultrapurification of mercury from associated impurities. Webelieve that a more promising method to obtain ultrapure mercury is multistageelectrolysis that can be performed in electrolyzers with bipolar mercuryelectrodes.
Further methods of purification and ultrapurification of mercury, includingvacuum distillation and multi-stage electrolysis, were described in considerabledetail by Kozin.3
References
1. S. M. Melnikov, Metallurgy of Mercury, Metallurgiya, Moscow, 1971.2. A. A. Saukov, Geochemistry, Gosgeolizdat, Moscow, 1950.3. L. F. Kozin, Physico-Chemistry and Metallurgy of High-Purity Mercury
and Its Alloys, Naukova Dumka, Kiev, 1992.4. L. F. Kozin, Amalgam Metallurgy, Tekhnika, Kiev, 1970.5. L. F. Kozin, Physicochemical Basics of Amalgam Metallurgy, Nauka,
Alma-Ata, 1964.6. L. A. Niselson and A. G. Yaroshevsky, High-Purity Substances, 1988, 6,
8–20.7. P. P. Pugachevich, Handling Mercury in Laboratory and Industrial
Conditions, Khimiya, Moscow, 1972.8. N. N. Rozanov, Collected Scientific Papers, Giredmet, Metallurgizdat,
Moscow, 1959, vol. 1, pp. 779–788.
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9. J. Soucek, Chem Listy, 1964, 58, 1203.10. L. N. Kuzmenkov, Studies in the Field of Physico-Chemical Measurements,
Standards Publishing, Moscow, 1968, Issue 96/156, pp. 79–91.11. A. G. Stromberg and I. Bykov, Zavod. Lab., 1953, 19, 171.12. L. F. Kozin and A. V. Abrosimov, Electrode Processes in Solid and Liquid
Electrodes, Nauka, Alma-Ata, 1964, vol. 12, p. 194.13. S. V. Ptitsin, J. Tech. Phys., 1935, 5, 309.14. M. C. Wilkinson, Chem. Rev., 1972, 72, 575.15. C. L. Gordon and E. Wichers, Ann. N. Y. Acad. Sci., 1957, 65, 369.16. L. F. Kozin, Bulletin of Inventions, 1960, (5), 38–39; Author’s Certificate
126 613, USSR.17. A. A. Sunier and C. M. White, J. Am. Chem. Soc., 1930, 52, 1842.18. G. A. Hulett and H. D. Minchin, Phys. Rev., 1905, 21, 388.19. A. A. Sunier and C. B. Hess, J. Am. Chem. Soc., 1928, 50, 662.20. C. J. Moore, J. Am. Chem. Soc., 1910, 32, 971.21. W. M. Spicer and C. J. Banick, J. Am. Chem. Soc., 1953, 75, 2268.22. F. Kobza and K. Grudina, Method for Mercury Treatment from Organic
Substances, 15 September 1987; Author’s Certificate 244 495 Czechoslovakia.23. G. Milazzo and S. Caroli, Tables of Standard Electrode Potentials, Wiley,
New York, 1978.24. D. Dobosh, Electrochemical Constants, Mir, Moscow, 1980.25. S. G. Bratsch, J. Phys. Chem. Ref. Data, 1989, 18, 1.26. A. M. Sukhotin (ed.), Handbook of Electrochemistry, Khimiya, Leningrad,
1981.27. W. M. Latimer, Oxidation States of Elements and Their Potentials in
Aqueous Solutions, Foreign Literature Publishing, Moscow, 1954.28. N. E. Khomutov, Elektrokhimiya, 1964, 1, 7–58.29. R. N. Goldberg and L. G. Hepler, Chem. Rev., 1968, 68, 229.30. V. A. Lebedev, V. I. Kober and L. F. Yamschikov, Thermochemistry of
Alloys of Rare-Earth Metals and Actinide Elements, Handbook, Metal-lurgiya, Chelyabinsk, 1989.
31. L. F. Kozin, S. P. Bukhman and Z. N. Nysakbaeva, Electrodes andElectrolytes, Izv. Akad. Nauk Kazakh., Ser. Khim., 1967, (15), 112.
32. S. P. Bukhman, Cementation by Metal Amalgams, Nauka, Alma-Ata, 1986.33. L. F. Kozin, Kinetics and Electrode Processes in Aqueous Solutions,
Naukova Dumka, Kiev, 1983, pp. 37–63.34. L. F. Kozin, T. I. Saprykina and A. T. Zamulyukin, Izv. Akad. Nauk
Kazakh., Ser. Khim., 1972, (2), 72–77.35. I. Leden, Acta Chem. Scand., 1952, 6, 971.36. M. G. Smirnova, V. A. Smirnov and L. I. Antropov, Research Papers
Novocherkas Polytech. Inst., 1956, 34/48, 69–75.37. A. N. Frumkin and F. J. Service, Zh. Fiz. Khim., 1930, 1, 52–64.38. L. F. Kozin and N. I. Ivanchenko, Izv. Akad. Nauk Kazakh., Ser. Khim.,
1975, 3, 84–90.39. V. M. Foliforov and V. S. Gorovits, Application of Magnetohydrodynamic
and Electrohydrodynamic Devices in Industrial Power and Metallurgy,
78 Chapter 4
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Publishing House of the Institute for High Temperatures of the USSRAcademy of Sciences, Moscow, 1989, pp. 27–39.
40. R. Krolikiewicz, K. Karwotski and A. Szmidkowski, Pol. Pat., 133 028,Polish Patent Bulletin, 1986, No.10.
41. V. Grmela, Chem. Zvesti, 1966, 20, 615.42. V. G. Artamonov, Zavod. Lab., 1965, 31, 254.43. V. G. Prihodchenko and O. V. Bogmat, Bulletin of Inventions, 1964, (4), 38;
Author’s Certificate 160 588, USSR.44. G. D. Klinsky, A. F. Mazenko, D. A. Knyazev, et al., Bulletin of
Inventions, 1985, (32), 120; Author’s Certificate 1 175 971, USSR.45. L. F. Kozin, Amalgam Pyrometallurgy, Nauka, Alma-Ata, 1973.46. L. F. Kozin, R. Sh. Nigmetova and M. B. Dergacheva, Thermodynamics of
Binary Amalgam Systems, A Nauka, lma-Ata, 1977.47. A. S. Russell and D. C. Evans, J. Chem. Soc., 1925, Pt. 2, 2221.48. D. Knokhe, East Ger. Pat., 207 311, Patent Bulletin, 1984, (8).49. L. F. Kozin, A. G. Morachevsky and I. A. Shcheka, Ukr. Khim. Zh., 1989,
55, 495.50. E. Newberg and S. M. Naube, Trans. Electrochem. Soc., 1933, 64, 189.51. F. A. Feryanchich, Tr. Komis. Anal. Khim. Akad. Nauk SSSR, 1947, 2, 87.52. J. R. Lorenz, KFKI Kozlemenyek, 1964, 12, 329.
Purification of Mercury Using Chemical and Electrochemical Methods 79
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CHAPTER 5
Chemical Properties of Mercury
5.1 Inorganic Mercury Compounds
Chemical compounds of mercury and metallic mercury have been widely studiedin theoretical and applied inorganic and organic chemistry, in electrochemistryand in the instrumentation industry. Many compounds of mercury possessextraordinary and valuable properties (physical and chemical) on the one hand,but on the other hand, they are extremely toxic and, thus, hazardous for theenvironment. The chemical and physical properties of mercury compounds havebeen extensively studied and a considerable amount of quantitative data has beenobtained and will be discussed in this chapter. A number of reviews1–10 havecovered the analysis of mercury and its compounds.
5.1.1 Disproportionation in Hg2þ2 and Hg21
A peculiar feature of the chemistry of Hg2X2 compounds is the ability of Hg2þ2ions to exhibit disproportionation (disprop) in the presence of excess Cl– and
Br– ions, and also some ligands in solution. The Hg2þ2 ion forms stable
complexes with OH–, S2–, CN– and I– ions and molecules of amines and alkyl
sulfides. Under these conditions, the Hg2þ2 ions disproportionate according to
Hg2þ2ðaqÞ"Hg2þðaqÞþHg0ðaqÞ ð5:1Þ
with an equilibrium constant
Kdisprop¼Hg2þ� ��
Hg0ðaqÞ�
�Hg2þ2
� ¼ 5:5� 10�9M ð5:2Þ
The ratio between the concentrations of Hg21 and Hg2þ2 ions in the presence of
metallic mercury in solution, i.e., Hg2þ� �
= Hg2þ2� �
in the Hg0 �Hg2þ2 �Hg2þ
Mercury Handbook: Chemistry, Applications and Environmental Impact
By Leonid F Kozin and Steve Hansen
r L F Kozin and S C Hansen 2013
Published by the Royal Society of Chemistry, www.rsc.org
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system, is equal to 0.0183 according to some citations1–4 and 0.0060–0.0120according to Sidgwick.5
If the solubility of free metallic mercury in water is taken into account [whichaccording to Sidgwick5 is 3.0�10–7M and (3.01� 0.12)�10–7mol kg–1], thenKdisprop¼ (1.8–5.5)�10–9M. Moser and Voigt6 described in detail the equi-
librium in the Hg�Hg2þ2 �Hg2þ system at an ionic strength of 0.05–0.1 M and
different concentrations of Hg2þ2 (0.38–1.52)�10–5M and Hg0 (1.1–3.2)�10–7Mand flow rates of clean nitrogen (1.5–2.5Lmin–1). The disproportionationreaction is rapid. Elementary mercury that is generated in this reaction is easilycarried off by the air flow from the water solution to the gaseous phaseaccording to
Hg0ðaqÞ �!k
HgðgasÞ ð5:3Þ
where k is a velocity constant that characterizes the generation of Hg1 in thevelocity-driving stage of the disproportionation reaction. The role of thedisproportionation reaction of Hg(I) ions in the process of carrying mercury tothe atmosphere was discussed by Toribara et al.8 The velocity of Hg(I) iondisproportionation follows the equation
VHg2þ2¼�
d�Hg
2þ2
�
dt¼
kKdisprop
�Hg
2þ2
��Hg
2þ� ð5:4Þ
The values of k were determined in a separate experiment. The results ofstudies of the disproportionation reaction of the Hg(I) ion in the temperaturerange 238–308K are given in Table 5.1. Kdisprop was calculated using solutions
with an ionic strength of m¼ 0.1 and Hg2þ2� �
¼ 7:6�106 M saturated with
metallic mercury at each temperature.
5.1.2 Solubility of Metallic Mercury in Water
Values of the solubility of metallic mercury have been studied over a broadrange of temperature. Experimental data in the temperature range278.15–407.95K are given in Table 5.2.
According to Sanemasa,10 the solubility of metallic mercury in water at298 K is 3.2�10–7M, whereas Glew and Hames11 suggested a value of
Table 5.1 Reaction rate constants and disproportionation equilibriumconstants of Hg2
21 ions at various temperatures.7
T(K) k (min–1) kKdisprop�109 (min–1) Kdisprop�109 (M)
238 1.7� 0.1 8.2� 0.5 4.8� 0.1293 2.0� 0.1 16� 1 7.9� 0.1298 2.2� 0.1 23� 2 11� 1303 2.3� 0.1 36� 1 16� 1308 2.5� 0.1 55� 1 22� 1
Chemical Properties of Mercury 81
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Table 5.2 Solubility of metallic mercury in water.
T(K) T (1C)
Mercury solubility
Ref.g-atom L–1
(mol L–1)mg L–1
(ng g–1, ppb)mg g–1
(ppm)xHg�109(mole fraction)
mg per100mL
278.15 5 9.57E–08 19.2 0.0192 1.72 0.00192 10283.15 10 1.38E–07 27.7 0.0277 2.49 0.00277 10293.15 20 2.24E–07 45 0.045 4.04 0.0045 10303.15 30 4.05E–07 81.3 0.0813 7.30 0.00813 10313.15 40 6.83E–07 137 0.137 12.3 0.0137 10323.15 50 1.09E–06 218 0.218 19.6 0.0218 10333.15 60 1.83E–06 368 0.368 33.1 0.0368 10343.15 70 2.79E–06 560 0.56 50.3 0.056 10353.15 80 4.24E–06 850 0.85 76.3 0.085 10373.15 100 5.98E–06 1200 1.2 107.8 0.12 10393.15 120 8.97E–06 1800 1.8 161.7 0.18 10298.15 25 3.15E–07 63 0.063 5.7 0.01 13a
308.15 35 5.43E–07 109 0.109 9.8 0.01 13a
323.15 50 8.82E–07 177 0.177 15.9 0.02 13a
338.15 65 1.08E–06 217 0.217 19.5 0.02 13a
353.15 80 1.30E–06 261 0.261 23.4 0.03 13a
363.15 90 1.67E–06 334 0.334 30.0 0.03 13a
298.15 25 2.99E–07 60 0.060 5.4 0.01 6298.15 25 3.05E–07 61.2 0.061 5.5 0.0061 12313.15 40 5.12E–07 103 0.103 9.2 0.0104 12323.15 50 7.43E–07 149 0.149 13.4 0.0150 12333.15 60 1.078E–06 216 0.216 19.4 0.0216 12343.15 70 1.333E–06 267 0.267 24.0 0.0267 12353.15 80 1.637E–06 328 0.328 29.5 0.0328 12307.15 34.0 3.61E–07 72 0.072 6.5 0.0072 16307.15 34.0 3.55E–07 71 0.071 6.4 0.0071 16307.65 34.5 4.44E–07 89 0.089 8 0.0089 16312.45 39.3 5.55E–07 111 0.111 10 0.0111 16312.95 39.8 5.55E–07 111 0.111 10 0.0111 16327.15 54.0 6.66E–07 134 0.134 12 0.0134 16330.65 57.5 8.33E–07 167 0.167 15 0.0167 16331.65 58.5 1.11E–06 223 0.223 20 0.0223 16333.45 60.3 9.99E–07 200 0.200 18 0.0200 16333.45 60.3 6.66E–07 134 0.134 12 0.0134 16333.45 60.3 9.44E–07 189 0.189 17 0.0189 16351.95 78.8 1.22E–06 245 0.245 22 0.0245 16362.75 89.6 2.44E–06 490 0.490 44 0.0490 16363.65 90.5 2.16E–06 434 0.434 39 0.0434 16364.45 91.3 2.00E–06 401 0.401 36 0.0401 16364.45 91.3 1.78E–06 356 0.356 32 0.0356 16375.15 102.0 2.11E–06 423 0.423 38 0.0423 16375.15 102.0 2.11E–06 423 0.423 38 0.0423 16375.15 102.0 2.22E–06 445 0.445 40 0.0445 16377.35 104.2 2.72E–06 546 0.546 49 0.0546 16380.65 107.5 3.05E–06 612 0.612 55 0.0612 16404.65 131.5 5.77E–06 1158 1.158 104 0.1158 16407.65 134.5 5.05E–06 1013 1.013 91 0.1013 16407.95 134.8 5.11E–06 1024 1.024 92 0.1024 16
aOriginal data were corrected by a factor of 1000.
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3.05�10–7M. As stated by Hepler and Olofsson,1 the solubility of metallicmercury in water in the temperature range 273.15–393.15K is described by theequation
logXHg¼� 43:3343� 20:9053 = T = 100 Kð Þ þ 15:7778ln T = 100 Kð Þ ð5:5Þ
with a standard deviation of 3.9�10–9 mole fraction of mercury (xHg). Valuesfor the solubility of mercury in water over the temperature range 277–343Kgiven by Choi and Tuck12 are close to those in Table 5.2. According to Choiand Tuck,12 the solubility of mercury in water follows the equation
logmHg¼� 126:345þ 4715:2
Tþ 42:0288logT ð5:6Þ
where m¼moles Hg–1000 gH2O–1, over the temperature range 273.15–
393.15K (0–120 1C).13 Figure 5.1 summarizes the data on the solubility ofmercury in water.10
The solubility of mercury in water at various temperatures and pressures ingiven in Table 5.3.17 Inversion of the solubility in water and in NaCl solutiontakes place at 54 1C. Systematic studies of the solubility of metallic mercury insolutions of electrolytes (NaCl, NaOH) were conducted by Chviruk andco-workers.18–21 Analysis of the data on mercury solubility in a logS–1/Tcoordinate system must correlate the experimental points with a straight linehaving a slope corresponding to the Henry constant.
Figure 5.1 Comparison of the solubilities of the mercury in pure water as a functionof temperature.Adapted from Refs. 6, 10, 12, 13, 16.
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At 298 K (25 1C), the solubility of mercury in water is (2.93–3.15)�10–7M.
Therefore, the difference in values for Kdisprop of Hg2þ2 ions in water must be
small and should depend mainly on the accuracy of determination ofmercury(I) and -(II) ion concentrations and their proportion. Moser and Voigt6
found that Kdisprop at 298K is equal to (1.1� 0.1)�10–8M, which is twice thevalue of Kdisprop¼ 5.5�10–9M reported by Sidgwick.5 This difference ofKdisprop values may be due to specifics of the experiments related to thedispersion of mercury even in the presence of traces of surfactants.
5.1.3 Solubility of Mercury in Ionic Solutions
The solubility of Hg2Cl2 in water depends on the concentration ofchloride ions:
Hg2Cl2ðsolidÞ ! Hg2þ2 þ 2Cl� ð5:7Þ
and, therefore, Kdisprop of reaction (5.1) will also change. The thermodynamicequilibrium constant of reaction (5.7) is Ks¼ (1.42� 0.02)�10–18.10 Thompsonet al.9 demonstrated that relatively high concentrations of mercury(I) ions in
the presence of liquid mercury cause the Hgliquid–Hg2þ2 –Hg21 system to
produce colloidal mercury. The high concentrations of mercury(I) ions in thedisproportionation reaction shift the equilibrium of reaction (5.1) to the leftand cause Kdisprop to decrease. Atoms of mercury should be in equilibrium
Table 5.3 Solubility of mercury in water at elevated temperatures andpressures.17
T (K) T (1C) P (atm) P (bar)
Mercury solubility
g kg–1 mol kg–1xHg�109(mole fraction)
573 300 500 507 0.29 0.0014 0.0260573 300 640 648 0.24 0.0012 0.0216571 298 900 912 0.19 0.0009 0.0171673 400 400 405 3.37 0.0168 0.302673 400 500 507 2.76 0.0138 0.248673 400 495 502 3.22 0.0161 0.289673 400 700 709 2.47 0.0123 0.222673 400 700 709 2.80 0.0140 0.251671 398 920 932 2.23 0.0111 0.200674 401 910 932 2.13 0.0106 0.191773 500 500 507 24.12 0.1202 2.16775 502 510 517 23.71 0.1182 2.12773 500 520 527 20.21 0.1008 1.81768 495 755 765 18.45 0.0920 1.65780 507 700 709 19.90 0.0992 1.78771 498 990 1003 16.36 0.0816 1.47776 503 960 972 13.41 0.0667 1.20
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with Hg2þ2 and Hg21 ions to obtain the true Kdisprop value in the system
Hg(aq)–Hg2þ2 –Hg21.
Equilibrium in the Hgliquid–Hg2þ2 –Hg21 system is established very quickly.
Ions of Hg2þ2 are easily created during the reduction of mercury(II) salts and are
easily oxidized to Hg21 and reduced to the metallic state. The reduction of
Hg2þ2 to Hg0 is determined by positive half-reaction potentials towards many
metals and reagents. Table 5.4 gives standard half-reaction potentials and
ratios between Hg2þ2 and Hg21 ions in the system Hg0–Hg2X2–HgX2�4 .
Standard electrode potentials may be used to calculate the ratios aHg2þ
2=Hg2þ
and aHg2þ =Hg2þ
2, using the equation
lnK� ¼ ln
aHg2þ
aHg2þ2
!¼
2F E0Hg2þ
2
� E0Hg2þ
2 =Hg2þ
� �
RTð5:8Þ
Table 5.4 Standard half-reaction potentials, temperature coefficients
(dE1/dT) and ratios of ions Hg2þ2 /Hg21 and Hg21/Hg2þ2 .
Half-reaction E1 (V) Ref.dE1/dT(mV K–1)
Hg2þ2Hg2þ
Hg2þ
Hg2þ2
Acid solutions
Hg2þ2 þ2e� ! 2Hg 0.789 22 – 1.66�102 6.02�10–3
2Hg2þþ2e� ! Hg2þ2 0.920 22 – 1.66�102 6.02�10–3
Hg2þþ2e� ! 2Hg 0.854 22 – 1.66�102 6.02�10–3
Hg2þ2 þ2e� ! 2Hgliq 0.796 22 –0.327 6.13�103 1.63�10–4
2Hg2þþ2e� ! Hg2þ2 0.908 22 0.095 6.13�103 1.63�10–4
Hg2þþ2e� ! Hgliq 0.852 22 –0.116 6.13�103 1.63�10–4
Hg2Br2þ2e� ! 2Hgþ 2Br� 0.1390 22 –0.142 2.55�102 3.92�10–3HgBr2�4 þ2e
� ! Hgþ 4Br� 0.210 23 –0.42 2.55�102 3.92�10–3
HgBr2�4 þe� ! HgBr�2 þ2Br� 0.281 24 – 2.55�102 3.92�10–3
Hg2I2þ2e� ! 2Hgþ 2I� –0.0405 22 0.019 1.48 0.67
HgI2�4 þ2e� ! Hgþ 4I� –0.040 24 0.04 1.48 0.67
HgI2�4 þe� ! HgI�2 þ2I� –0.0395 24 – 1.48 0.67
HgSO4þ2e� ! 2HgliqþSO2�4
0.61257 25 –0.826 – –
Hg2ðSCNÞ2þ2e� ! 2Hgliqþ2SCN� 0.22 23 – – –
HgðCNÞ2�4 þ2e� ! Hgliqþ4CN� –0.37 23 0.78 – –
HgðCNÞ2þ2e� ! Hgþ 2CN� –0.304 23 – 7.25�108 1.38�10–9
HgðCNÞ2þ2e� ! 2Hgþ 2CN� –0.435 23 – 7.25�108 1.38�10–9
HgSðSolid redÞþ2Hþþ2e� ! HgliqþH2S –0.096 1 – – –
HgSðsolid blackÞþ2Hþgasþ2e� ! HgliqþH2S –0.085 1 – – –
Hg2ðN3Þ2ðsolidÞþ2e� ! 2Hgliqþ2N�3 0.260 1 – – –
Hg2CO3ðsolidÞþ2e� ! 2HgliqþCO2�3
0.309 1 – – –
Hg2Ac2ðsolidÞþ2e� ! 2Hgliqþ2Ac� 0.51163 1 0.8995 – –
HgðCNÞ2þe� ! HgCN�2 –0.173a – – –
aObtained by the analytical method developed by Chviruk and Koneva.20
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Contact of Hg21 ions with metallic mercury creates Hg2þ2 ions as a result of
the reproportionation reaction
Hgliquid þHg2þ"Hg2þ2 ð5:9Þ
Equilibrium in the Hg–Hg2X2–HgX2 system also depends on both the natureof the ligands (X¼Cl–, Br–, I–, ClO4
–, SO42–, Ac–, etc.) and their concentration.
If no ligands are present in the solution, the equilibrium of reaction (5.9) ataHgliquid ¼ 1 will shift to the right to achieve the ratio
K ¼aHg2þ
2
aHg2þ¼ 1:66�10�2 ð5:10Þ
Introduction of Hg0liquid–Hg2X2–HgX2 into a solution of halides and other
ligands leads to changes of the standard electrode potentials of mercury half-reactions and shifts their values towards the negative side as seen in Table 5.4.At the same time, Keqn (5.9) values decrease and Keqn (5.8) values increase.Notably, the standard electrode potentials of mercury in the presence of ligandsthat form stable mercury complexes (CN–, I–) acquire negative values.According to Hepler and Olofsson,1 the dissociation constant of themercury(I) ion:
Hg2þ2ðaqÞ"HgþðaqÞ ð5:11Þ
is Ko10–7. This K value allows HgþðaqÞ ions to register directly, with the help of
electron spin resonance spectra, in mercury(I) perchlorate solutions.
Thermodynamic parameters for the formation of Hg2þðgasÞ and Hg2þ2ðgasÞ ions at
298.15K, according to Vanderzee and Swanson,26 are given in Table 5.5.
5.2 Mercury(I) and Mercury(II) Halides and
Pseudohalides
The synthesis of mercury halides is well known and was summarized by Simonet al.27 Calomel can be produced by sealing a mixture of mercury andmercury(II) chloride in iron or fused-silica tubes and heating at 525 1C.A cooled condenser is attached that receives calomel vapor condensate.28,29
Synthesis from the elements is also possible.30 Very finely divided mercury(I)
Table 5.5 Thermodynamic parameters for the formation of Hg2þðgasÞ and
Hg2þ2ðgasÞ ions at 298.15K.26
Ion DG�form (kJ mol–1) DH�form (kJ mol–1) S� (J mol–1 K–1)
Hg2þ2 153.607� 0.105 166.816� 0.210 –65.816� 0.837
Hg2þ 164.703� 0.105 170.163� 0.210 –36.233� 0.837
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chloride can also be obtained by precipitation from a dilute nitric acid solutionof mercury(I) nitrate and sodium chloride.28
Mercury(II) chloride can be synthesized from the elements in sealed andheated vessels, such as quartz. Mercury is oxidized with chlorine; the reactionoccurs with flames at temperatures4300 1C. The reaction product is condensedin cooled collectors as fine crystals. Calomel is not formed when excess chlorineis present.30
Mercury and chlorine also react in the presence of water; in this case,intensive stirring is necessary. The chloride formed precipitates as crystals afterthe solubility limit has been exceeded. If an alkali metal chloride solution isused in place of water, solutions of chloro complex salts are formed, which areused mainly for the production of other compounds of divalent mercury.31
Mercury(II) chloride can also be prepared from other mercury compounds.Mercury(II) sulfate, for example, is heated in the dry state with sodium chlorideand the evolved mercury(II) chloride vapor is condensed to a solid in receivers.In another synthesis method, a warm sublimate solution is obtained from thereaction of mercury(II) oxide and a stoichiometric amount of hydrochloricacid; the chloride separates as crystals on cooling.27
HgBr2 is produced from mercury and bromine in the presence of water bydissolution of mercury(II) oxide in hydrobromic acid or by precipitation from anitric acid solution of mercury(II) nitrate with addition of sodium bromide.32
Methods for the synthesis of HgI2 are similar to those for mercury(II)bromide.33-35
5.2.1 Mercury(I) Fluoride – Hg2F2
Physical properties of Hg2F2 are given in Table 5.6. In the solid state, Hg2F2
forms yellow tetragonal crystals, which quickly darken when exposed to light.Mercury(I) fluoride hydrolyzes in water into HF and unstable mercury(I)hydroxide and disproportionates:
2HgOH! HgþHgðOHÞ2 ð5:12Þ
HgðOHÞ2"HgOþH2O ð5:13Þ
Hg2F2 is more soluble than Hg2Cl2 in water; however, the literature providesno reliable information concerning its solubility.3,4
Figure 5.2 illustrates the coordination of Hg2X2 (X¼F, Cl, Br, I).
5.2.2 Mercury(II) Fluoride – HgF2
HgF2 forms colorless crystals with a cubic structure and lattice parametera¼ 0.555 nm.44 Each Hg atom in the lattice is surrounded by eight closely setatoms of fluorine (z¼ 8). HgF2 is synthesized by exposing Hg2F2 to chlorine at543K or NOF�3HF at 473K. Mercury(II) fluoride, HgF2, can also be obtainedvia reaction of gaseous fluorine with HgCl2 or HgBr2. Mercury(II) fluoride
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easily forms a dihydrate, HgF2�2H2O. The dihydrate has a density of5.72 g cm–3,24 and crystallizes in an orthorhombic unit cell.
In dilute HF solutions (0–4.3%), the solubility in the HgOþHFþH2Osystem at 298K has shown that the solid phase is HgO.45 Equilibrium of thesame system in concentrated HF (5.9–100%) has shown that at 5.9–18.4% HFthe solid-state phase is HgOHF and at 23.6–76.7% HF it is HgF2�H2O.46 Thesolubility of HgO decreases from 15.0 to 2.8% as the HF concentrationincreases from 23.6 to 76.7%. Of all of the mercury halides, only mercury(II)fluoride is dissociated in aqueous media. It forms unstable complexes in thesystem Hg(II)–F–. The ion formation constant in the reaction
Hg2þ þ F�"HgFþ ð5:14Þ
according to Aylett3 equals 10 and according to Hepler and Olofsson1 equals
38. The thermodynamic properties of the hydrated ion HgFþðaqÞ have been
published.1,47 Table 5.7 gives physical and thermodynamic properties of HgF2.Values of DG�f and DH�f for Hg2X2 decrease as the transition from fluorides
to iodides occurs. However, DS�298:15 increases in the same sequence. The molar
heat capacity of mercury(I) halides depends only slightly on the nature of the
Table 5.6 Physical properties of Hg2F2.
Property Value Ref.
Molecular weight (gmol–1) 439.18Tmelt (K) decomposes4843K 36H�f ;298:15 (kJmol–1) –492 at 25 1C 37
G�f ;298:15 (kJmol–1) –437.5 at 10 1C 38
S�298:15 (J mol–1 K–1) 40 (estimated) 1Crystal structure Tetragonal 39Color Yellow 36
Distances:d(Hg–Hg) (nm) 0.243 40
0.251 410.243 420.253 36
d(Hg–X) (nm) 0.241 400.214 410.231 42
d(X–X) (nm) 0.385 40
Figure 5.2 Structures of halides Hg2X2 (X¼F, Cl, Br, I). Bond angles are not exactly180 1.Reproduced with permission from Ref. 43.
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halide. Overviews of the physical properties of mercury fluorides haveappeared.46,49 Although mercury(I) fluorides are poisonous, they are widelyused for the fluorination of organic compounds.
5.2.3 Mercury(I) Chloride (Calomel) – Hg2Cl2
The thermodynamic and physical properties of Hg2Cl2 are given in Table 5.8.Hg2Cl2 forms colorless tetragonal crystals: z¼ 2, a¼ 0.445 nm, c¼ 1.089 nm.40
X-ray diffraction analysis of solid mercury(I) halides demonstrates that they allhave a similar structure, in which each atom of mercury creates an interatomicbond with two closest located atoms of halide. The melting point(under pressure) is 798K (525 1C). As a result of disproportionation, mercury(I)chloride sublimes by decomposing into Hg and HgCl2 at 656.25K (383.7 1C):
Hg2Cl2ðgasÞ ! HgCl2ðgasÞ þHgðgasÞ ð5:15Þ
The enthalpy of this reaction is DHdisprop¼ –506.26 kJmol–1.3 Therefore,only an extremely strong Hg–Hg bond is able to stabilize the gaseous dimer
Hg2þ2 (or Hg2Cl2), whereas the monomer HgCl will be subject to dispro-
portionation. Given that, the phase transformation (melting, boiling)temperatures determined using standard methods will not be correct. There isno doubt that intensive mercury(I) halide disproportionation reactions occurat much lower temperatures than the phase transformation temperatures,which introduces an error into transformation temperature measurements.In addition, Hg2Cl2, just as other mercury(I) halides, especially mercury(I)iodide, decomposes through a disproportionation reaction when exposedto light. Mercury(I) chloride oxidizes to HgCl2 under the effect of Cl2 or FeCl3.SO2, SnCl2 and Fe(II) restore HgCl2 to Hg2Cl2. The solubility productof Hg2Cl2 between 278.15 and 318.15K may be calculated4,50 using theequation
logKs¼� 17:884 � 0:017ð Þ þ 0:0622 � 0:0002ð Þ T � 298:15ð Þ
� 3:0 � 0:2ð Þ � 10�4 T � 298:15ð Þ2mol kg�1 ð5:16Þ
Values obtained through this equation agree well with published experimentaldata for Ks.
4 The observed solubility of Hg2Cl2 in saturated solutions at
Table 5.7 Physical properties of HgF2.
Property Value Ref.
Molecular weight (gmol–1) 238.39Melting point, (K) decomposes4918 36DHmelt (kJmol–1) 23.0� 4.2 48Density (g cm–3) 8.95 (15 1C) 39Crystal structure Cubic 36
Chemical Properties of Mercury 89
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298.15K is (7.5� 0.3)�10–6M.30 According to Marcus,50 the solubility ofHg2Cl2 is calculated to be (8.4� 1.0)�10–6M.
The solubility product of Hg2Cl24 at several temperatures is given in Table 5.9.
The relationships between logKsp and 1/T for Hg2Cl2 and other mercury(I)halide solubility products are linear over a wide temperature range. Experi-mental data are in good agreement with the calculated solubility product.
5.2.4 Mercury(II) Chloride (Corrosive Sublimate) – HgCl2
Mercury(II) chloride forms colorless orthorhombic crystals with latticeparameters z¼ 4, a¼ 0.5963 nm, b¼ 1.2735 nm and c¼ 0.4325 nm.6 The vaporpressure of mercury(II) chloride vapor pressure57 is found through the equation
ln PHgCl2 ðPaÞ� �
¼ 28:17� 9531
Tð5:17Þ
Dry HgCl2 is stable when exposed to air. When solutions boil, mercury(II)chloride fumes escape with water vapor. Aqueous solutions of mercury(II)
Table 5.9 Solubility product of Hg2Cl2 (adapted from Ref. 4).
T (K) T (1C) Ks (mol3 kg–3)
278.15 5.00 (5.65� 0.22)�10–20298.15 25.00 (1.433� 0.056)�10–18318.15 45.00 (1.738� 0.068)�10–17
Table 5.8 Physical properties of Hg2Cl2.
Property a-Hg2Cl2 b-Hg2Cl2 Ref.
Molecular weight (gmol–1) 472.086Ferroelastic transition (K) 185 51Tmelt (K) 798a 51Density (g cm–3) 7.18 52H�f ;298:15 (kJmol–1) –265.6 1
G�f ;298:15 (kJmol–1) –210.8 1
S�298:15 (Jmol–1K–1) –183.8 1
Refractive index:n0 1.96 53ne 2.62 53Crystal structure Tetragonal 51
Distances (nm)d(Hg–Hg) 0.260 40
0.245 36d(Hg–Cl) 0.236 40
0.252 540.241 55
d(Cl–Cl) 0.333 540.370 55
aConstrained pressure.
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chloride have been the subject of many studies. The results of experimentsperformed to test the solubility of mercury(II) chloride in water and differentelectrolytes have been summarized.4 Solubility values for HgCl2 in water arelisted in Table 5.10.
The recommended value for the solubility in water at 298.15K (25 1C) is0.269� 0.003mol kg–1. The solubility of HgCl2 between in the temperaturerange 273.15–378.15K (0–105 1C) is expressed by the equation
log HgCl2½ � ¼ � 56:7732þ 64:4481
T
100
� � þ 29:7574lnT
100
� �mol kg�1 ð5:18Þ
and in the range 383–508K (110–235 1C) by the equation
log HgCl2½ � ¼ � 14:7003� 51:8426
T
100
� �mol kg�1 ð5:19Þ
The calculated solubility is smaller than the experimental values listed givenby Skinner et al.34 at 298.15K, greater at 303.15–368.15K and again smaller at373–378K. The deviation is� 3.5%. Experimental and calculated solubilities ofmercury(II) chloride, bromide and iodide in water versus the inverse oftemperature feature a break in the lnm–1/T plot.91 Plots for mercury(I)chloride, bromide and iodide versus inverse of temperature are straight lines.91
Mercury(II) chloride is practically undissociated in aqueous solutions.Equilibrium reaction constants are as follows:4
HgCl2ðformÞ"HgþðaqÞ þ 2Cl�ðaqÞ Kform eqn 5:20ð Þ ¼ 7:1�10�15M ð5:20Þ
HgCl2ðformÞ"HgCl2ðaqÞ Kform eqnð5:21Þ ¼ 0:11M ð5:21Þ
The ions HgClþ, HgCl2, HgCl�3 and HgCl2�4 are generated in aqueous
solutions with free chloride ion concentrations between 1�10–3 and 1.0M.92–96
Equilibrium reaction constants for these ions are as follows:
Hg2þ þX�"HgXþ K1; DH1ð Þ ð5:22Þ
HgXþ þX�"HgX2 K2; DH2ð Þ ð5:23Þ
HgX2 þX�"HgX�3 K3; DH3ð Þ ð5:24Þ
HgX�3 þX�"HgX2�4 K4; DH4ð Þ ð5:25Þ
Hg2þ þ 2X�"HgX2 b2; DHb� �
ð5:26Þ
Hg2þ þ 2X�"HgX2�4 b4 = b3; DH3 þ DH4ð Þ ð5:27Þ
Hg2þ þ 4X�"HgX2�4 b4; DHb4
� �ð5:28Þ
Chemical Properties of Mercury 91
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Table 5.10 Solubility of mercury(II) chloride in water (adapted from Ref. 4).
T (K) T (1C)Molality, mHgCl2
(mol kg–1 H2O) Ref.
273.15 0.00 0.21 58273.15 0.00 0.16 59273.25 0.10 0.149 60274.05 0.90 0.173 61277.65 4.50 0.185 60278.15 5.00 0.1707 62280.65 7.50 0.197 60283.15 10.00 0.1920 62283.15 10.00 0.193 63286.95 13.80 0.201 60288.15 15.00 0.2164 62288.15 15.00 0.211 64288.71 15.56 0.206 65289.15 16.00 0.26 58291.15 18.00 0.229 66293.15 20.00 0.272 67293.15 20.00 0.242 64293.15 20.00 0.320 63293.15 20.00 0.2407 62294.05 20.90 0.244 61298.15 25.00 0.266 68298.15 25.00 0.272 69298.15 25.00 0.273 70298.15 25.00 0.267 71298.15 25.00 0.271 72298.15 25.00 0.269 73298.15 25.00 0.267 74298.15 25.00 0.2596 75298.15 25.00 0.268 64298.15 25.00 0.2658 76298.15 25.00 0.272 77298.15 25.00 0.2658 78298.15 25.00 0.269 61298.15 25.00 0.27 79298.15 25.00 0.273 80298.15 25.00 0.265 81298.15 25.00 0.2711 62298.15 25.00 0.263 82298.15 25.00 0.257 83298.25 25.10 0.281 60302.65 29.50 0.302 60303.15 30.00 0.305 84,85303.15 30.00 0.305 86307.15 34.00 0.344 87308.15 35.00 0.342 88308.15 35.00 0.345 89308.15 35.00 0.331 81311.15 38.00 0.401 60312.35 39.20 0.380 61317.15 44.00 0.45 58318.15 45.00 0.424 81
92 Chapter 5
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where X�¼Cl–, Br–, I–. MeX2�mm =X� can be found from the following
equations:
K1¼HgXþ½ �
Hg2þ� �
X�½ �ð5:22aÞ
K2¼HgX2½ �
HgXþ½ � X�½ �ð5:23aÞ
K3¼HgX�3� �HgX2½ � X�½ � ð5:24aÞ
Table 5.10 (Continued)
T (K) T (1C)Molality, mHgCl2
(mol kg–1 H2O) Ref.
322.15 49.00 0.467 60328.95 55.80 0.566 61329.15 56.00 0.581 87334.15 61.00 0.651 60335.85 62.70 0.687 61348.55 75.40 0.995 61353.15 80.00 1.13 60353.15 80.00 1.12 87360.15 87.00 1.44 60364.75 91.60 1.612 61372.85 99.70 2.110 61373.15 100.00 2.38 60373.15 100.00 2.07 87378.2 105.05 2.35 90378.8 105.65 2.773 61389 115.85 3.54 90394 120.85 5.45 60396 122.85 4.56 90400 126.85 8.47 60402 128.85 5.88 90406 132.85 6.87 90413 139.85 12.3 60414 140.85 8.84 90418 144.85 10.06 90423 149.85 13.3 60430 156.85 14.7 90432 158.85 14.9 60433 159.85 16.4 60437 163.85 17.5 60438 164.85 16.5 60448 174.85 23.6 90455 181.85 29.2 90468 194.85 39.1 90479 205.85 48.9 90496 222.85 67.1 90508 234.85 88.4 90
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K4¼½HgX2�
4 �½HgX�3 �½X��
ð5:25aÞ
b2¼K1K2¼HgX2½ �
Hg2þ� �
X�½ �2ð5:26aÞ
b4 = b2¼K3K4¼HgX2�
4
� �
HgX2½ � X�½ �2ð5:27aÞ
b4¼K1K2K3K4¼HgX2�
4
� �
Hg2þ� �
X�½ �4ð5:28aÞ
The interaction of mercury(II) ions in the course of reactions (5.25)–(5.31) isattended by a change in enthalpy, which, in a 3M solution of NaClO4, is asgiven in Table 5.11.97
The standard thermodynamic functions of chloride complexes ofmercury(II), according to different authors, differ considerably, as illustrated inTable 5.12 for two sets of results.1,97
Table 5.13 compares the known equilibrium constants (logKi) for differentreactions taking place in Hg(II)–Cl– systems.92–95 The consecutive constants ofreactions (5.22)–(5.26) differ widely among themselves, which is due to thespecifics and accuracy of the different methods used, and also differentconcentrations of the solutions. The complex formation constants K1, K2,. . ., Ki
Table 5.11 Change in enthalpy of mercury(II)ions in a 3M solution of NaClO4.
97
Parameter DH (kJ mol–1)
DH1 –24.23� 1.00DH2 –27.15� 1.51DH3 –4.31� 0.88DH4 –6.19� 1.00DHb2 –51.38� 1.13DH3þDH4 –10.50� 0.50DHb4 –61.88� 1.26
Table 5.12 Standard thermodynamic functions of chloridecomplexes of mercury(II).1,97
Species Ref.
DG�form; 298:15(kJ mol–1)
DH�form; 298:15(kJ mol–1)
S�form; 298:15(J mol–1 K–1)
HgCl3½ �� 1 308.8 389.5 205.097 314.5� 1.1 381.1� 0.7 252.4� 4.4
HgCl4½ �2� 1 446.4 554.8 289.097 449.0� 1.2 558.4� 0.9 288.4� 5.0
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for HgX z�mð Þ�m (z¼ 2; m¼ 1–4) given by Hepler and Olofsson1 and Clever et al.4
are in good agreement with the data presented in the literature.92–96
Consecutive constants are of great importance for reactions producingHgCl1 and HgCl2 (m¼ 1 and 2). The equilibrium constant, K2, involved in theformation of HgCl2 via the reaction
HgClþ þ Cl�"HgCl2 ð5:29Þ
is more than 3.7�105 times greater than K3 for the reaction
HgCl2 þ Cl�"HgCl�3 ð5:30Þ
Notably, K14K2cK34K4, whereas K1 is comparable to K2 and K3 to K4. Sucha relationship is also characteristic of other halides (Br–, I–) and ions.
Table 5.17 gives the formation constants for the mercury(II) complexesformed with F–, Cl–, Br–, CN– and SCN– ions, according to Hepler andOlofsson.1 It should be mentioned that the sequence F–, Cl–, Br–, I–, CN– is
characterized by increasing complex ion formation constants for HgX z�mð Þ�m ,
which is due to increasing deformability of X– ions from F– through CN–.Mercury(II) halides, HgX2, are practically undissociated in aqueous
solutions, as mentioned above, yet if exposed to excess alkali metal halides,MeX (Me¼Na, K, Rb, Li), or saturated solutions of ammonium halides theyform highly soluble and dissociated complexes Me2[HgX4] and (NH4)2�[HgX4]:
2MeXþHgX2"Me2 HgX4½ � ð5:31Þ
Me2 HgX4½ �"Me2þ þHgX2�4 ð5:32Þ
2NH4ClþHgX2" NH4ð Þ2 HgX4½ � ð5:33Þ
The effect of chloride ions on the formation of dissociated forms ofcomplexes is illustrated in Figure 5.3, depicting the production of mono-, di-,tri- and tetrachlorides of mercury(II) as a function of concentration of freechloride ions.98 The aqueous solubility of dihalides increases at the same time.Thus, the poorly soluble mercury(II) iodide does dissolve if exposed to excessmercury salts, producing particles [Hg–I–Hg]31. This property of mercurydihalides is exploited when designing electrolytes needed to obtain high-puritymercury.
Table 5.13 Equilibrium constants for the system Hg(II)–Cl�.43,61,93,94
Equation LogKi 298K43 298 K61 298K93 295� 1K94
(5.22) LogK1 6.73� 0.98 – 6.72� 0.02 –(5.23) LogK2 6.30� 0.02 – –(5.24) LogK3 0.85� 0.15 0.95� 0.03 1.00� 0.01 1.25� 0.25(5.25) LogK4 – – – 1.36� 0.25(5.26) LogK3K4 0.85� 0.05 2.00� 0.05 1.97� 0.05 2.65� 0.50
Chemical Properties of Mercury 95
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The solubility of mercury(II) halides in organic solvents is given in Table 5.14.Physical properties of HgCl2 are summarized in Table 5.15.
5.2.5 Mercury(I) Bromide – Hg2Br2
Physical properties of Hg2Br2 are given in Table 5.16. Solid Hg2Br2 formscolorless tetragonal crystals with z¼ 2, a¼ 0.465 nm and c¼ 1.110 nm.109
It does not form hydrates.54 Hg2Br2 dissolves when heated in concentratednitric acid, hot concentrated sulfuric acid or hot ammonium carbonatesolution. Hg2Br2 is less soluble than Hg2Cl2 in water. The recommendedsolubility product Ks at 298.25 is 6.40�10–23mol kg–3 H2O.4 The temperaturedependence of the mercury(I) bromide solubility product at zero ionic force canbe calculated using the equation
lgKs¼ 55:306� 235:22ðT=100Þ � 25:195 lnðT=100Þmol3 kg�3 ð5:34Þ
Table 5.14 Molar solubility of Hg(II) halides in organic solvents at 25 1C.
Solvent HgCl2 HgBr2 HgI2 Ref.
Benzene 16�10–3 16�10–3 7.5�10–3 100Benzene 15.6�10–3 16.6�10–3 101Diethyl ether 0.170 67�10–3 8.3�10–3 100Acetone 3.22 0.96 31�10–3 100Acetonitrile 1.83 0.26 7.6�10–3 100Methanol 2.0 1.5 68�10–3 100Dimethyl sulfoxide 2.00 3.25 4.25 100Pyridine 0.90 0.80 0.70 100Piperidine 44�10–3 0.97 1.20 100Chloroform 2.2�10–3 3.2�10–3 101Toluene 22.1�10–3 22.7�10–3 101o-Xylene 34.9�10–3 38.2�10–3 101
Figure 5.3 Yield of complex ions of mercury(II) as a function of free chloride ionconcentration.Reproduced with permission from Ref. 99.
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obtained via regression analysis of known experimental data97,110,111 andsummarized by Clever et al.4
The Hg–Br phase diagram (Figure 5.4)112 shows the phase relations betweenHg and Br. Mercury(II) bromide forms by a congruent reaction with liquidwhereas Hg2Br2 forms by a syntectic reaction between L1 and L2. Liquiduspoints are from Dworsky and Komarek.115 The phase diagrams of Hg–Cl andHg–I are similar.113,114
Figure 5.5 illustrates the environment of mercury in the structure ofmercury(II) chloride, bromide and iodide.
Table 5.18 provides experimental data values for the solubility of mercury(I)bromide in water. These data are internally consistent. According toTable 5.18, as the ionic force increases, the Hg2Br2 solubility productincreases from 6.40�10–23 at m¼ 0 to 670�10–23 at m¼ 3.1, where m is theionic force. Mercury(I) bromide is obtained via anodic dissolution of mercuryin HBr, by exposing Hg2(NO3)2 solution to KBr in nitric acid. Hg2Br2 isused in electrolytes used to refine mercury, electrochemical experiments,optoacoustic bulk devices, organomercuric compound synthesis, organiccatalysis, etc.
5.2.6 Mercury(II) Bromide – HgBr2
Solid HgBr2 forms colorless orthorhombic crystals with lattice parametersz¼ 4, a¼ 0.679 nm, b¼ 1.2445 nm and c¼ 0.4624 nm.109 Its vapor pressure wasdetermined.121 The vapor pressure of liquid HgBr2
121,122 is also well known.
Table 5.15 Physical properties of HgCl2.
Property Value Ref.
Molecular weight (g mol–1) 271.495Melting point (K) 553 36DHsublimation (kJ mol–1) 80.8 102
77.4 10383.1 104
Boiling point (K) 591 36Critical temperature (K) 972 105Density (g cm–3) 5.44 56H�f ;298:15 (kJ mol–1) –225.9 1
–229.2 106–226.0 107
G�f ;298:15 (kJ mol–1) –180.3 1
S�298:15 (J mol–1 K–1) –152.9 1Color White 36Crystal structure Orthorhombic 108
Distances (nm):d(Hg–Cl) 0.229 56d(Cl–Cl) 0.333 56Cl–Hg–Cl bond angle (1) 178.9 56
*Calculated.
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In aqueous solution, HgBr2 forms complex solutions in which the followingforms are in equilibrium: Hg21, Br–, HgBr1, HgBr2
0, HgBr3–, HgBr4
2– andHgOH1. HgBr2
0 molecules prevail in aqueous solution. HgBr2 exhibits a highsolubility in water4 if samples contain traces of HBr. This is due to complexformation in the system Hg(II)–Br–. The aqueous solubility of mercury(II)bromide is lower than that of mercury(II) chloride, being 1.70�10–2 mol kg–1 at298.15K. Solubility can be found from the following equation in thetemperature interval 273–353K:
lnmHgBr2 ¼ 5:3570� 28:096T
100
� �mol kg�1 ð5:35Þ
and at higher temperatures using
lnmHgBr2 ¼ 85:918� 380:791T
100
� �mol kg�1 ð5:36Þ
Table 5.19 gives experimental solubility values for HgBr2 in water attemperatures between 273.15 and 474K. From analysis of the experimentaldata, it was found that within the temperature ranges 273.15–437K (0–164 1C)and 437–509K (164–236 1C) the solubility curves of log[HgBr2] versus 1/T havedifferent temperature coefficients. The solubility curves intersect at 437K.A sharp increase in the solubility of HgBr2 in water occurs at temperatures
Table 5.16 Physical properties of Hg2Br2.
Property a-Hg2Br2 b-Hg2Br2 Ref.
Molecular weight (g mol–1) 560.988Ta-b (ferroelastic transition) (K) 143 51Tmelt (K) 727.35 (decomp.) 115DHsublimation (kJ mol–1) 84.1 112Tboil (K) 618 (sublimes) 112Density (g cm–3) 7.307 116H0
f ;298:15 (kJ mol–1) –206.94 1
G0f ;298:15 (kJ mol–1) –181.08 117
118S0298:15 (J mol–1 K–1) 86.7 1
ColorRefractive index:n0 2.12 119ne 2.98 119Crystal structure Tetragonal 54
Distances (nm)d(Hg–Hg) 0.258 54
0.250 55d(Hg–Br) 0.249 120
0.253 540.245 55
d(Br–Br) 0.271 1200.340 540.355 55
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above 437K (164 1C). A temperature rise of only 28 1C (from 446 to 474K)increases the solubility 458-fold. This effect has the following explanation.Clearly, the sharp increase in the solubility of HgBr2 in water is due to theacid–base interaction that occurs in the course of dissociation of mercury(II)bromide and formation of Hg21 and Br–. Br– and HgBr2 exhibit acidic
Figure 5.4 The Hg–Br phase diagram. Hg2Br2 forms by a syntectic reaction (L1þL2
- Hg2Br2). Hg2Cl2 and Hg2I2 also form in the same type ofreaction.112–114 Liquidus data points are from Ref. 115.
Figure 5.5 Environment of mercury in the crystal structure of (a) HgCl2, (b) HgBr2and (c) HgI2.Reproduced with permission from Ref. 43.
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properties, whereas Hg21, with basic properties, creates complexes Hg[HgBr3]1
and Hg[HgBr4] with greater water solubility.Table 5.19 demonstrates the large change in the solubility of HgBr2 with
temperature. Clever et al.4 calculated the HgBr2 solubility product at 298.15Kto be Ks¼ 6.2�10–20mol3 kg–3, which is in good agreement with the valuereported by Iwamoto et al.129
A study of the reaction equilibrium:
Hg2þ þHgBr2"2HgBrþ ð5:37Þ
demonstrated that the equilibrium constant:
K12¼HgBrþ½ �2
Hg2þ� �
HgBr2½ �ð5:38Þ
equals 6.6� 0.2.97 Mercury(II) bromide is also practically undissociated. Thereaction equilibrium:
HgBr2ðsolidÞ"Hg2þ þ 2Br� ð5:39Þ
Table 5.18 Experimental values of the mercury(I) bromide solubility productin aqueous solution as a function of temperature.
T (K) T (1C) Ks (mol kg–1) Ref.
283.95 10.80 0.545�10–23 123288.05 14.90 1.00�10–23 123288.15 15.00 0.968�10–23 124292.35 19.20 3.89�10–23 123293.15 20.00 2.56�10–23 124298.15 25.00 5.50�10–23 123298.15 25.00 6.43�10–23 124299.65 26.50 6.95�10–23 123303.15 30.00 15.21�10–23 124308.15 35.00 35.85�10–23 124313.15 40.00 81.33�10–23 124318.15 45.00 177.6�10–23 124
Table 5.17 Formation of mercury(II) complexes at 298.15K according toRefs 1 and 110.
Reaction Ki
Formation constant
F – Cl – Br – I – CN – SCN –
Hg2þþX� ! HgXþ K1 38 5.8�106 1.1�109 6.4�1012 2.0�1017 1�109
HgXþþX� ! HgX2 K2 – 2.5�106 2.5�108 1.3�1011 1.7�1017 1�108HgX2þX� ! HgX�3 K3 – 6.7 1.5�102 6.2�103 5.5�103 7�102HgX�3 þX� ! HgX2�
4K4 – 13 23 1.1�102 1.0�103 7�101
Hg2þþ4X� ! HgX2�4
b4 – 1.3�1015 9.2�1020 5.6�1029 1.9�1041 5�1021
Hg2þþ2X� ! HgX2b2 – 1.45�1013 2.75�1017 – – –
HgX2þ2X� ! HgX2�4
b4b2 – 8.96�101 3.35�103 – – –
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is shifted to the left. The equilibrium of the reverse reaction in aqueous solutioncontaining 3.0 and 0.5M ClO4
–:
Hg2þ þ Br� þH2O! HgBrðOHÞ þHþ ð5:40Þ
is complicated by hydrolysis.1 In aqueous solutions with a free bromide ionconcentration of 1�10–3–1.0M, the following forms of HgBr2 are created:HgBr2, HgBr3
– and HgBr42–. The reaction equilibrium constants for eqns
(5.22)–(5.29), where X–¼Br–, are given in Table 5.17. The physical propertiesof HgBr2 are given in Table 5.20.
Mercury(II) bromide is fairly soluble in organic solvents. Table 5.17 givessolubility data for HgCl2, HgBr2 and HgI2 in several organic solvents.Mercury(II) bromide is also soluble in acetone, benzene and carbon disulfidebut poorly soluble in diethyl ether. It is used as a catalyst in organic synthesisand analytical chemistry and in the production of high-purity mercury.
5.2.7 Mercury(I) Iodide – Hg2I2
Physical properties of mercury(I) iodide are given in Table 5.21. SolidHg2I2 forms tetragonal crystals with parameters z¼ 2, a¼ 0.492 nm andc¼ 1.161 nm.133 Mercury(I) iodide disproportionates into Hg and HgI2 whenexposed to light. It has a weak solubility in water: the most credible value for
Table 5.19 Mercury(II) bromide solubility in water as a function oftemperature (adapted from Ref. 4).
T (K) T (1C) Molarity (mol dm–3) Molality (mol kg–1) Ref.
273.15 0.00 0.008 125277.65 4.50 0.0075 126283.55 10.40 0.0119 126293.15� 1.0 20.00 0.00223 127298.15 25.00 0.017 70298.15 25.00 B0.011 68298.15 25.00 0.0167 72298.15 25.00 0.017 73298.15 25.00 0.017 74298.15 25.00 0.0170 128298.15 25.00 0.0170 126298.15 25.00 0.017 83307.15 34.00 0.02 125353.15 80.00 0.08 125415 141.85 0.378 90437 163.85 0.801 90446 172.85 1.40 90458 184.85 4.01 90460 186.85 8.72 90461 187.85 16.4 90462 188.85 54.8 90466 192.85 166 90474 200.85 641 90
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the solubility product at 298.15K is Ks¼ 5.2�10–29mol3 kg–3.1,110 From 283 to298K the solubility product can be found from the equation
logKsðHg2I2Þ ¼ � 30:72þ 0:094 T � 273:15ð Þmol3kg�3 ð5:41Þ
and between 273.15 and 373.15K the following equation is suggested:
logKsðHg2I2Þ ¼ � 3:5483� 7347
Tþ 0:0044logT þ 0:293
� 10�3T mol3kg�3ð5:42Þ
Table 5.20 Physical properties of HgBr2.
Property Value Ref.
Molecular weight (gmol–1) 360.40Melting point (K) 511 115Boiling point (K) 591 36Density (g cm–3) 6.08 4DG�f ;298:15 (kJmol–1) –153.1 130
DH�f ;298:15 (kJmol–1) –170.7 1
–175.5 131–166.2� 4 107
DS�298:15 (Jmol–1K–1) 167 1Color Colorless as solution Yellow as liquid 36Crystal structure Orthorhombic 132
Distances (nm):d(Hg–Hg) 40d(Hg–Br) 40d(Br–Br) 40
Table 5.21 Physical properties of Hg2I2.
Property Value Ref.
Molecular weight (g mol–1) 654.989Tmelt (K) 570 (decomp.) 113DH fusion (kJmol–1) 10.32 133Density (g cm–3) 7.78 134H0
f ;298:15 (kJmol–1) –121.34 130
–123.2� 8 135G0
f ;298:15 (kJmol–1) –111.0 130
S0298:15 (Jmol–1K–1) 233.5 130
Crystal structure Tetragonal 1
Distances (nm):d(Hg–Hg) 0.269 54d(Hg–I) 0.268 54d(I–I) 0.355 54
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Table 5.22 gives results for Ks Hg2I2ð Þ.
Mercury(I) iodide does not form hydrates. It disproportionates in potassiumiodide solutions through the reaction
Hg2I2 þ 2KI"K2 HgI4½ � þHg0 ð5:43Þ
with Kdisprop¼ 0.67. Hg2I2 may be synthesized by exposing Hg (in excess) toHgI2 at To563K or by reacting HgCl2 with stannous chloride in an alcoholicsolution of KI. Hg2I2 dissolves in castor oil and aqueous ammonia solution butdoes not dissolve in ethanol and diethyl ether.
5.2.8 Mercury(II) Iodide – HgI2
The physical properties of mercury(II) iodide are given in Table 5.25.Table 5.23 lists solid-state transformations. The vapor pressures of solid andliquid HgI2 have been published.122,123,136 The different crystal structures ofmercury(II) iodide are quite complex. The current Hg–I phase diagram hasbeen drawn correctly,46 but the true complexity of the various metastable formsof HgI2 is not apparent. The metastable yellow (yellowM) and orange(orangeM) forms produced from solution growth are mechanically unstable andtransform into the red form (stable at room temperature and pressure). Orangecrystals, when heated to 127 1C, will transform into the stable high-temperatureyellow (yellowHT) form of HgI2.
The red to yellow transformation occurs with a heat of transition of2.68–2.85 kJmol–1.142,143 Mercury(II) iodide does not form hydrates.Table 5.24 gives the aqueous solubility of HgI2 at various temperatures.Figure 5.6 shows the HgI2–H2O phase diagram.90
5.2.8.1 Yellow HgI2
There are two yellow polymorphs of HgI2: one is metastable at roomtemperature, designated yellowM, and the other is the stable high-temperatureform, yellowHT. The metastable yellow form is formed at room temperature bysublimation or by crystallization from solution. The high-temperature yellowform results from a phase transition at 127–130 1C. The metastable yellow
Table 5.22 Solubility product of mercury(I) iodide in aqueous solution(adapted from Ref. 4).
T (K) T (1C) Ks�1029 (mol3 kg–3) Ref.
283.15 10.0 2.01�1030 123288.05 14.9 5.10�1030 123292.35 19.2 1.05�1029 123298.15 25.0 4.95�1029 123
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structure contains almost linear (178.31) I–Hg–I chains and has an ortho-rhombic structure. Under pressure, both the orange and metastable yellowforms of HgI2 transform into the red HgI2 structure, although by different
Table 5.23 Solid-state phase transformations in mercury(II) iodide.137
Transformation Crystal structure ColorTransitiontemperature (1C) Ref.
a-HgI2 - b-HgI2 Tetragonal -monoclinic
Red - yellowHT 127–130 138,139
YellowM-HgI2 -a-HgI2
Orthorhombic -tetragonal
YellowM - red 25 35, 139,140
OrangeM-HgI2 -a-HgI2
Tetragonal -monoclinic
Orange -yellowHT
127 140,141
Table 5.24 Aqueous solubility of mercury(II) iodide as a function oftemperature (adapted from Ref. 4).
T (K) T (1C) CHgI2 (mol dm–3) Molality (mol kg–1) Ref.
291� 2 17.85� 2 7.4�10–5 144290.65 17.50 8.87�10–5 145295.15 22.00 1.18�10–4 145295.65 22.50 2.2�10–4 146298.15 25.00 B1.3�10–4 68298.15 25.00 9.77�10–5 147298.15 25.00 1.05� 0.055�10–4 148298.15 25.00 1.3�10–4 83373.15 100.00 4.0�10–3 149469 195.85 8.1�10–2 90502 228.85 0.21 90514 240.85 0.25 90
Figure 5.6 HgI2–H2O phase diagram.Reproduced with permission from Ref. 90. Copyright r 1937 VerlagGmbH & Co. KGaA, Weinheim.
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mechanisms.138 The crystal structure of the stable high-temperature yellowform is monoclinic.139
5.2.8.2 Orange HgI2
Three forms of orange HgI2 are built from Hg4I10 supertetrahedra. Two formsare polytypic structures141 and the third form is created from interpenetratingthree-dimensional networks of Hg4I10 supertetrahedra. The two polytypicstructures are built on Hg4I10 supertetrahedra linked at each corner.
Experimental values for the solubility of HgI2 in water are listed inTable 5.24. A critical assessment of the literature data was performed on thesolubility of mercury(II) iodide in water.4 Its solubility in the temperatureinterval 288–323K can be determined with the equation
lnmHgI2 ¼ 7:608� 49:576T
100
� �mol kg�1 ð5:44Þ
and in the temperature interval 463–513K using
lnmHgI2 ¼ 10:751� 64:134T
100
� �mol kg�1 ð5:45Þ
The physical properties of HgI2 are given in Table 5.25. The temperaturecoefficients of the HgI2 solubility curves, in coordinates of logm versus 1/T, upto the transition temperature from the tetragonal red to monoclinic yellowmodification at 400K (127 1C), do not differ much between themselves. This isdue to the small change in dissolution enthalpy, 41 kJ mol–1, for the tetragonalred modification and 52 kJ mol–1 for the monoclinic yellow modification.4 At514K (241 1C), the HgI2–H2O system goes through a transition fromsolid–liquid to liquid–liquid. As can be seen from the HgI2–H2O phasediagram90 (Figure 5.6), the system achieves full miscibility at 611K (338 1C)
Table 5.25 Physical properties of HgI2.
Property a-HgI2 Red b-HgI2 Yellow Ref.
Molecular weight (g mol–1) 454.40Melting point (K) 530.15 113DHa-b (kJmol–1) 2.9� 0.02 142
2.85� 0.02 143DHb-melt (kJmol–1) 18.8 150DSmelt (Jmol–1K–1) 35.98DHsublimation (kJmol–1) 85.8 102
85.5 104Boiling point (K) 624 36Density (g cm–3) 6.30 6.38 151DH�f ;298:15 (kJmol–1) –105.4 –102.9 130
DG�f ;298:15 (kJmol–1) –101.7 130
DS�298:15 (Jmol–1K–1) 180.0 130Crystal structure See text
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and 77% HgI2. The HgCl2–H2O, HgBr2–H2O and Hg(CN)2–H2O systems donot feature areas of liquid–liquid immiscibility.90
Calculation of the solubility product of HgI2 by Clever et al.4 andYatsimirsky and Shutov152 are in very close agreement at 298.15K. The solu-bility product is Ks¼ 2.9�10–29mol3 kg–3. The relationship between the solu-bility product and temperature can be calculated using the equation
logKs¼� 3:276� 182:765 =T
100
� �mol3kg�9 ð5:46Þ
within an accuracy of 15%.4 Mercury(II) iodide is moderately soluble inorganic solvents also is also soluble in dioxane, chloroform and aqueous KIsolution. The stability constant of mercury complexes formed via the reaction
Hg2þ þ 4X�" HgX4½ �2� ð5:47Þ
increases with increasing deformability of anions in the sequence X�¼Cl–, Br–,I– (b4¼ 1.3�1015, 9.2�1020 and 5.6�1029, respectively). Formation constants of
the complex HgX 2�mð Þ�m for equations (5.22)–(5.29) are given in Table 5.17.
5.2.9 Mixed Mercury(II) Halides
Equilibrium constants of the halide exchange reaction:1
HgX2ðaqÞ þHgY2ðaqÞ"2HgXYðaqÞ ð5:48Þ
where X, Y¼Cl–, Br– and I–, are listed in Table 5.26.Equilibrium constants (K) of the exchange reaction at 298 K:1,2,152,158–161
HgBr2�4 þ nI! HgBr4�nIn½ �2�þnBr� ð5:49Þ
with n¼ 1, 2, 3 and 4 are given in Table 5.27.HgI2 is an important commercial material. It is used in X-ray and g-ray
detectors, metal halide lamps, electrochemical experiments, production ofelectrolytes needed to obtain high-purity mercury and analytical chemistry(e.g., saturated K2[HgI4]) and Ba[HgI4] solutions).
5.2.10 Mercury(II) Cyanide – Hg(CN)2
The physical properties of Hg(CN)2 are given in Table 5.28. Mercury(II)cyanide decomposes at 693K (420 1C) into mercury and cyanogen. Earlyattempts to obtain Hg2(CN)2 only succeeded in producing Hg(CN)2 and
Table 5.26 Equilibrium constants and properties of mixed mercury(II) halides.
Mixed halide LogK153 LogK154 Density (g cm–3)155 Color
HgBrI 1.07� 0.08 1.10� 0.20 Yellow–orange156
HgClI 1.35� 0.17 1.75� 0.20HgClBr 1.14� 0.11 2.0� 0.5 5.72� 0.19 White157
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metallic mercury as a result of a disproportionation reaction. Some researchersbelieve that Hg2(CN)2 can be obtained in non-aqueous solutions at lowtemperatures.162 Hg(CN)2 forms white tetragonal crystals with C–Hg–C bondangles of 1711.163,164 It exhibits high water solubility, 93 g kg–1 H2O at 287Kand 539 g kg–1 H2O at 373K.
Aqueous solutions of mercury(II) cyanide contain fully undissociatedmolecules Hg(CN)2. The equilibrium constant for the dissociation of Hg(CN)2:
HgðCNÞ2"Hg2þ þ 2CN� ð5:50Þ
is 2.9�10–35. The equilibrium constant of the reaction
HgðCNÞ2 ! Hg2þ þ 2CN� ð5:51Þ
is 1.9�1014.1,97 The equilibrium constants of exchange reactions of the type
HgðCNÞ2 þHgðXÞ2 ! 2HgXðCNÞ ð5:52Þ
where X�¼Cl�, Br� and I� have been published,167,168 and for X–¼ I– is0.11167 or 0.14.168
The equilibrium constants of cyanide complexes depend on theircomposition,1,169as seen in the following equations:
HgðCNÞ2Cl� þ CN� ! ½HgðCNÞ3Cl�
2� K¼ 3:3� 103 ð5:53Þ
HgðCNÞ�3 þBr� ! ½HgðCNÞ3Br�2� K¼ 4:2 ð5:54Þ
Table 5.28 Physical properties of Hg(CN)2.
Property Value Ref.
Molecular weight (g mol–1) 252.62Melting point (K) 320 C (decomp.) 165Density (g cm–3) 3.996 (25 1C) 166DH�f ;298:15 (kJmol–1) 263.6 130
Crystal structure Tetragonal 163,164
Distances (nm):d(Hg–C) 0.199 163,164d(Hg–N) 0.270 163,164
Table 5.27 Equilibrium constant in mixed halideexchange reaction (5.49).1,2,152–161
n Equilibrium constant
1 1.6�1032 3.1�1053 2.4�1074 6.0�108
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HgðCNÞ2þCl� ! ½HgðCNÞ2Cl�� K¼ 0:5 ð5:55Þ
HgðCNÞ�3 þCl� ! ½HgðCNÞ3Cl�
2� K¼ 0:3 ð5:56Þ
The resulting solutions that contain cyanide complexes, including misalignedones, are electrically conductive and are used in engineering. Electricallyconductive solutions can also be obtained by introducing excess sodiumcyanide or other alkali metal cyanides:
HgðCNÞ2 þ 2NaCN"2Naþ þHgðCNÞ2�4 ð5:57Þ
as background salts {K2[Hg(CN)4], Li2[Hg(CN)4], etc.}. Mercury(II) cyanidecan be obtained from mercury oxide and KFeIIFeIII(CN)6 according to
3HgOþKFeIIFeIIIðCNÞ6 þ 3H2O! 3HgðCNÞ2 þ FeðOHÞ2þ FeðOHÞ3 þKþ þOH� ð5:58Þ
when the mixture is heated at 363K (90 1C) for several hours.3 Hg(CN)2 can beisolated from the solution using standard operations. Mercury(II) cyanide ishighly soluble in various organic solvents.
5.2.11 Mercury(I) Dithiocyanate – Hg2(SCN)2
Mercury(I) dithiocyanate has an orthorhombic crystal structure with a¼ 1.571nm, b¼ 0.643 nm and c¼ 0.638 nm.170 It is poorly soluble in water. Whenanalyzing the experimental data concerning the solubility of mercury(I) thio-cyanate in water, one should take into account both the disproportionation
reaction of Hg2þ2 ions to Hg0 and Hg21 and the formation of complexes
HgSCN1, Hg(SCN)2, HgðSCNÞ�3 and HgðSCNÞ2�4 . According to experimental
data from the literature,1–4 the solubility of Hg2(SCN)2 in water at 298.15K is2.7�10–7mol dm–3. The solubility product of Hg2(SCN)2 in water at 298.15 isKs¼ 3.2�10–20 (Ref. 4) to 3.0�10–20.160
Hg2(SCN)2 is obtained via an exchange reaction by mixing a weakly acidicsolution of Hg(NO3)2 after contact with metallic mercury (in less than stoi-chiometric proportions) with KSCN solution. This first reaction produces adark green or dark gray precipitate, which, upon stirring in the dark, convertswithin a few days to Hg2(SCN)2. Hg2(SCN)2 is a white precipitate that issensitive to light. Hg2(SCN)2 is then isolated by filtering, rinsing a few times inboiling distilled water and drying in vacuum.171 Mercury(I) thiocyanatedisproportionates in KSCN solution through the reaction
Hg2ðSCNÞ2"Hg0 þHgðSCNÞ2 ð5:59Þ
5.2.12 Mercury(II) Dithiocyanate – Hg(SCN)2
The physical properties of mercury dithiocyanate are given in Table 5.29.Hg(SCN)2 has a greater solubility in water than Hg2(SCN)2. As with
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Hg2(SCN)2, to determine the solubility of mercury(II) dithiocyanate in waterone should take into account the formation of thiocyanate complexes ofmercury(II). The solubility of mercury(II) thiocyanate in water is 1.74�10–3mol m–3 at 293K172 and 2.2�10–3 mol dm–3 at 298 K. The solubility product is2.15�10–8.4
Tetrathiocyanatomercurates(II) of alkali metals, Me2[Hg(SCN)4], are fairlysoluble in water and ethanol and have high electric conductivity.Me2[Hg(SCN)4] is obtained by dissolving Hg(SCN)2 in a boiling solution ofaqueous KSCN. Mercury sulfide is produced as the solution cools, is filteredoff and the filtrate is stripped in the normal way. Dazzling white crystals ofMe2[Hg(SCN)4] are produced.173 Divalent ions of heavy metals Zn21, Cd21,Cu21, Co21, Pb21 and Mn21 combine with[Hg(SCN)4]
2– anions to createpoorly soluble Me[Hg(SCN)4] salts, the solubilities of which at 293K is given inTable 5.30.
Mercury thiocyanate complexes of Zn,177 Co178 and other metals179 havebeen studied in detail.
5.3 Oxygen Compounds of Mercury(I) and Mercury(II)
Mercury reacts with oxygen to form mercury(I) oxide (Hg2O), mercury(II)oxide (HgO) and mercury peroxide (HgO2).
5.3.1 Mercury(I) Oxide – Hg2O
Hg2O is a thermally unstable compound and decomposes into HgO and Hgwhen exposed to light. Hg2O forms black crystals with d4¼ 9.8 g cm–3.Mercury(I) oxide is obtained by exposing mercury to water vapor at
Table 5.29 Physical properties of Hg(SCN)2.
Property Value Ref.
Molecular weight (g mol–1) 316.74Melting point (K) 438 (decomp.)a 27Density (g cm–3) 3.71 174
3.73 175DG�f ;298:15 (kJmol–1) –253.1a 176
Crystal structure Monoclinic 175
aDecomposition begins at 110 1C and is spontaneous at 165 1C (438K).
Table 5.30 Solubility of divalent ions at 293K in[Hg(SCN)4].2–4,158,159
Divalent ion Solubility at 293K (mol dm–3)
Zn21 1.75�10–4Cd21 19.0�10–4Cu21 1.82�10–4Co21 5.37�10–4Pb21 9.72�10–3Mn21 0.660
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temperatures below 373K. When hydroxide ions are added to solutions ofmercury(I) salts, a number of successive reactions take place in which theresulting hydroxides and oxides of mercury(I) were observed as short-livedintermediates:
Hg2þ2 þ 2OH� ! Hg2ðOHÞ2 ð5:60Þ
Hg2ðOHÞ2 ! Hg2OþH2O: ð5:61Þ
The resulting mercury(I) oxide disproportionates in the presence of waterthrough the reaction
Hg2Osol ! HgOsol þHgliq: ð5:62Þ
A disproportionation reaction inn solid Hg2O has been observed at 373K.The heat of disproportionation is 35.56 kJmol–1.180 The hydrolysis reaction
Hg2þ2 þH2O"Hg2ðOHÞþ þHþ ð5:63Þ
has an equilibrium constant of 1�10–5. Hg2O is poorly soluble in water,Ks¼ 1.6�10–23, but fairly soluble in nitric acid. The standard electrodepotential of the Hg2O/Hg half-reaction in alkaline solutions:
Hg2OþH2Oþ 2e! 2Hgþ 2OH� ð5:64Þ
is þ0.123 V (versus normal hydrogen potential). Numerous claims abouthaving obtained black Hg2O from solutions of mercury(I) salts and alkali arenot proven. X-ray diffraction, magnetic susceptibility testing and heat offormation measurements were used to prove that the product of the reaction is
a mixture of metallic mercury and mercury(II) oxide. A study of the Hg2þ2 /OH–
reaction equilibrium:
Hg2OHþ"k1
k�1Hg0 þHgOHþ ð5:65Þ
has shown that, when Kdisprop¼ k1/k–1¼ 5.5�10–9M and k–1¼ 9.0�107 mol–1 s–1,the disproportionation reaction rate constant k1¼ 0.495 s–1.162
5.3.2 Mercury(II) Oxide – HgO
HgO exists in two modifications, yellow and red. Thermodynamic andstructural values of the red and yellow modifications of HgO are given in Ref.181 and references contained therein. Both modifications are orthorhombiccrystals. The crystals have tetrahedral valence angles Hg–O–Hg and O–Hg–Oof 1091 and 1791, respectively, in z-shaped chains –Hg–O–Hg–O–. The Hg–Obond length is 0.203 nm and the shortest Hg–O– distance is 0.282 nm.182–184
Figure 5.7 illustrates the geometry of the Hg–O bonding in HgO.The density of the yellow modification is dyellow¼ 11.03 g cm–3 and that of
the red modification is dred¼ 11.14 g cm–3.182–184 HgO decomposes at 773K(500 1C) with a heat of þ180.9 kJmol–1. Red HgO turns black when heated but
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returns to its original color as it cools. Yellow HgO turns red when heated.At the atomic level, HgO crystals appear as endless chains of –O–Hg–O–Hg–O,with an –Hg–O–Hg– angle of 1091 and an –O–Hg–O– angle of 1801.185
Red HgO is synthesized by either a dry or a wet method. The dry methodconsists of oxidation of metallic mercury with oxygen or ozone at 573–673 K orcareful heating of Hg2(NO3)2 and Hg(NO3)2 at 623–673 K. In the wet method,mercury(II) oxide (HgO) is precipitated from hot mercury(II) salt solutionswith the help of hydroxides of alkali or alkaline earth metals. The resultinghydroxide of mercury(II), Hg(OH)2, on the introduction of alkali metalhydroxides, immediately decomposes into HgO and Hg2O. Mercury(II) oxidecan also be obtained via anodic dissolution of mercury in a solution ofhydroxides. Standard half-reaction potentials are as follows:
HgOred þH2Oþ 2e�"Hgþ 2OH� Eo ¼þ 0:0981V22;23 ð5:66Þ
HgOþ 2H2Oþ 2e� ! Hgþ 2OH� Eo¼þ 0:0966V22;23 ð5:67Þ
HgðOHÞ2 þ 2Hþ þ 2e� ! Hgþ 2H2O Eo¼þ 1:034V23 ð5:68Þ
2HgOþ 4Hþ þ 2e� ! Hg2þ2 þ 2H2O Eo¼þ 1:065V23 ð5:69Þ
2HgðOHÞ2 þ 4Hþ þ 2e� ! Hg2þ2 þ 4H2O Eo¼þ 1:279V23 ð5:70Þ
Yellow HgO is obtained by exposing mercury(II) solutions to alkali metalhydroxides. Mercury oxide powders exhibit maxima in IR absorption at v¼ 491and 595 cm–1 and become phosphorescent in the spectral range 2.0–4.5 eV. Theequilibrium constant for the reaction
HgOþH2O"HgðOHÞ2 ð5:71Þ
is B10–2. Mercury(II) hydroxide begins to precipitate at pHE2; completeprecipitation occurs as pHE5–12. The hydrolysis reactions are
Hg2þ þH2O! HgðOHÞ þHþ ð5:72Þ
HgðOHÞþ þH2O"HgðOHÞ2 þHþ ð5:73Þ
HgðOHÞ2 þOH�ðOHÞ�3 ð5:74Þ
HgOred þH2OðOHÞ�3 ð5:75Þ
Figure 5.7 Characteristic structure of HgO.Reproduced with permission from Ref. 43.
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Data for the solubility of HgO in water are given in Table 5.31. The solubilityproduct of Hg(OH)2 at 291K is Ks¼ 4�10–26mol dm–3.3 The solubility ofmercury(II) oxide in water depends on the size of the particles. Water–organicmedia (water–methanol, water–ethanol, water–2-propanol) have little effect onthe solubility of mercury(II) hydroxide.192 Thus, the solubility of Hg(OH)2 inwater, determined using a radioactive tracer technique, is 1.35�10–9 mol L–1
(Ks¼ 9.84�10–27) at 293.65 K. For a 1:1 solvent:solute ratio, the values are asgiven in Table 5.32.192
Mercury(II) hydroxide exhibits amphoteric properties. In acidic solutions itionizes through the following reactions:
HgðOHÞ2 ! HþþHHgO�2 ð5:76Þ
HHgO�2 ! HþþHgO2�2 ð5:77Þ
HgðOHÞ2 ! HgOHþþOH� ð5:78Þ
HgðOHÞ2 ! Hg2þþ 2OH� ð5:79Þ
HgOsolidþHþ ! HgOHþ ð5:80Þ
HgOsolidþ 2Hþ ! Hg2þþH2O ð5:81Þ
In alkaline solutions, the reactions are as follows:
HgOsolidþOH� ! HHgO�2 ð5:82Þ
HgOsolidþ 2OH� ! HgO2�2 þH2O ð5:83Þ
Table 5.31 Solubility of HgO in aqueous solution at25 1C (293K) (adapted from Ref. 186).
Solubility (�10–4 mol L–1) Ref.
Red Yellow2.26� 0.03 2.36� 0.03 186– 2.41 1872.34 – 1882.37 2.39 1892.33 – 1902.25 2.37 191
Table 5.32 Solubility of Hg(OH)2 in water–organicmedia.192
Component Solubility, S (�10–9 mol L–1) Ks
CH3OH 0.981 3.77�10–27C2H5OH 1.02 4.42�10–27C3H7OH 1.12 5.61�10–27
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The equilibrium constants of reactions (5.78)–(5.81) are described by thefollowing equations at 298.15K
K5:78¼xHgOHþxOH�
xHgðOHÞ2¼ 7:1� 10�12 mol dm�3 ð5:84Þ
K5:79¼xHg2þx
2OH�
xHgðOHÞ2¼ 2:2� 10�23 ðmol dm�3Þ2 ð5:85Þ
K5:80¼xHgOHþ
xHgþ¼ 0:17 ð5:86Þ
K5:81¼xHg2þ
x2Hþ¼ 53 ðmol dm�3Þ�1 ð5:87Þ
This is why the solubility of HgO depends on pH. At pH 10.4, the solubility ofHgOyellow is 4.64�10–4mol dm–3. The solubility of HgO as a function of acidityand alkalinity has been reported.193 Mercury(II) hydroxide starts to precipitateat pHE2 and stops at pHE5–12.194 Hg(OH)2 dissolves in concentratedalkaline solutions.
The structure of the Pourbaix diagram of equilibrium in the mercury–watersystem at 298.15 K is discussed in Ref. 195 and in acidic solutions in Ref. 196.The solubility of mercury(II) oxide in aqueous solutions of salts, as shown inTable 5.31, increases considerably.
Mercury(II) hydroxide dissolves in concentrated alkaline solutions and inHCl and HNO3, but does not dissolve in alcohols. For practical purposes, dataon the thermal stability of mercury(II) oxide are important. HgO starts todecompose at 903K (603 1C).46,180 At red heat, HgO completely sublimes intothe gas-phase constituents Hg and O2. The following equations were obtainedfor the dissociation pressure of HgO:180
logPSHgþO2¼ 10:9518� 5273:5
Tþ 1:75logT � 0:001033T Pa ð5:88Þ
Table 5.33 Thermodynamic properties of organic mercury compounds R2Hgand RHgX.
Compounda Name DH0form (kJ mol–1) Ref.
(CH3)2Hg (l) Dimethylmercury þ59.8 1CH3HgCl (c) Methylmercury chloride –119.6 212CH3HgBr (c) Methylmercury bromide –87.8 212CH3HgI (c) Methylmercury iodide –44.3 212C2H5HgCl (c) Ethylmercury chloride –142.2 213C2H5HgBr (c) Ethylmercury bromide –108.8 213C2H5HgI (c) Ethylmercury iodide –66.9 213C10H22Hg Diphenylmercury 282.8 1C6H5ClHg Phenylmercury chloride –2.3� 9.6 214
al¼ liquid, c¼ crystalline.
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logPO2¼ 206:07966� 27569
T� 57:581logT Pa ð5:89Þ
logPHg¼ 66:71495� 10529:8
T� 16:61logT Pa ð5:90Þ
Mercury peroxide, HgO2, is obtained from the reaction between the yellowmodification of mercury oxide with a 30% solution of H2O2 at 258 K or byadding H2O2 and K2CO3 to an alcoholic solution of HgCl2. If a dry synthesismethod is used, mercury oxide is fused, i.e., melted, with an alkali metalperoxide to obtain the colorless compound M2HgO2 (where M¼ alkali metal),which decomposes into the original components when it comes into contactwith water. M2HgO2 contains structural fragments [O–Hg–O]2–. Mercuryperoxide is barely stable and explodes upon heating or impact.
Mercury can form mixed valence compounds with halides, chalcogenides andother anions. Appendix III gives examples of mixed valence compounds. Aninteresting example is the crystal structure of an oxide–bromide ofmercury(I, II), Hg8O4Br3.
197 As can be seen in Figure 5.8, five atoms of Hg(I)(Hgl–Hg5) and three atoms of Hg(II) (Hg6–Hg8) are positioned asym-metrically. The atoms of mercury(I) form three pairs with interatomic Hg–Hgspacings of 0.2517(2)–0.2557(3) nm. These distances are somewhat greater thanthe spacings found in Hg(I) compounds.
5.3.3 Mercury(I) Nitrate Dihydrate – Hg2(NO3)2�2H2O
Mercury(I) nitrate dihydrate forms monoclinic, colorless crystals.198 Thecrystals contain Hg–Hg–OH2 chains with a bond angle of 167.51. A density of4.785 g cm–3 was reported by Grdenic.198 Dry mercury(II) nitrate, obtained by
Figure 5.8 Linkage of –O–Hg(I)–Hg(I)–O chains.Reproduced with permission from Ref. 197.
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Potts and Allred,199 decomposes into nitrogen oxide and a yellow product attemperatures above 373K. The infrared spectra of the latter showed that NO3
groups form dual coordination bonds with mercury. Studies of theHg2
21–NO3–H2O system suggests a weak complex with constant K1E1200 isdeveloped. Mercury(I) nitrate is obtained by exposing excess metallic mercuryto moderately concentrated nitric acid for several days, according to theequation
6Hgþ 8HNO3 ! 3Hg2 NO3ð Þ2þ2NOþ 4H2O ð5:91Þ
The resulting colorless short monoclinic crystals of Hg2(NO3)2�2H2O areseparated. Mercury(I) nitrate can also be obtained by heating metallic mercuryin excess in moderately dilute HNO3. Hg2(NO3)2�2H2O melts at 343K (70 1C);it hydrolyzes in the presence of excess water and produces the basic saltHg2(OH)(NO3). Acidic solutions of Hg2(NO3)2 are stable if they are notexposed to air or oxygen.
5.3.4 Mercury(II) Nitrate – Hg(NO3)2
Depending on the experimental conditions, mercury(II) nitrate forms anoctahydrate, Hg(NO3)2�8H2O, a monohydrate, Hg(NO3)2�H2O, and ahemihydrate, Hg(NO3)2�0.5H2O. Mercury(II) nitrate hemihydrate is the mosteasily obtained salt. Hg(NO3)2�0.5H2O melts at 352K (79 1C). Its crystals arecolorless, with a density of 4.30 g cm–3, and are sensitive to light. Attempts toobtain dry salt using a thermal method resulted in a basic salt, Hg3O2(NO3)2.Dry Hg(NO3)2 is produced via a reaction between N2O4 and HgO.3 Hg(NO3)2is slightly volatile in vacuum.
Mercury(II) nitrate exists in the form of almost completely undissociatedmolecules in aqueous solutions. It exhibits considerable solubility in diluteHNO3 or acetone. Nitrates are widely used for the synthesis of complexmercury(II) compounds. Mercury(II) nitrate is normally obtained by dissolvingmetallic mercury or mercury oxide in an excess of nitric acid:
3Hgþ 8HNO3 ! 3Hg2 NO3ð Þ2þ2NOþ 4H2O ð5:92Þ
Crystals of mercury(II) nitrate monohydrate are obtained by evaporating thesolution with subsequent crystallization. Hg(NO3)2 solutions are only stable inthe presence of a certain amount of nitric acid, which prevents hydrolysis.Hg(NO3)2 quickly hydrolyzes in excess water and produces a precipitate ofHg3O2(NO3)2�H2O or, when boiled in dilute solutions, forms mercury(II) oxide(HgO).3 There is experimental proof of complex formation200 occurringthrough the reactions
HgðNO3Þ2þNO�3 "HgðNO3Þ�3 ð5:93Þ
HgðNO3Þ�3 þNO�3 "HgðNO3Þ
2�4 ð5:94Þ
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5.3.5 Mercury(I) Perchlorate – Hg2(ClO4)2
Mercury(I) perchlorate has a molecular mass of 600.086 g mol–1 and forms twohydrates: Hg2(ClO4)2�4H2O and Hg2(ClO4)2�2H2O (at temperatures above309K). Hg2(ClO4)2 has an extremely high solubility in water. In such solutions,the perchlorate dihydrate, Hg2(ClO4)2�2H2O, is the stable phase upon contactwith a solution. Such solutions exhibit a tendency to hydrolyze (a 0.2Msolution has pH 2.1). Hg2(ClO4)2 is completely dissociated in aqueoussolutions. There is no information about the formation of dry Hg2(ClO4)2. Thehydrate Hg2(ClO4)2�n H2O is obtained by dissolving mercury(I) carbonate inperchloric acid or by electrolytic dissolution of metallic mercury in perchloricacid solutions of specific concentrations.200
5.3.6 Mercury(II) perchlorate – Hg(ClO4)2
Mercury(II) perchlorate also forms crystalline hydrates, Hg(ClO4)2�H2O,Hg(ClO4)2�2H2O and Hg(ClO4)2�6H2O.
Mercury(II) perchlorate crystallizes into hexagonal crystals of hexahydrate,which cannot be dehydrated by thermal means. Hg(ClO4)2 also exhibitsconsiderable water solubility: 2.980 kg Hg(ClO4)2 per kilogram H2O at298.15K. Aqueous solutions of Hg(ClO4)2 are highly acidic [0.5 M Hg(ClO4)2is hydrolyzed by 37%].3 The main product occurring during the hydrolysis ofaqueous solutions is a precipitate of Hg3O2(ClO4)2.
Perchlorate solutions exhibit good electrical conductivity and containhydrated ions Hg21 and HgOH1. Hg(ClO4)2 is obtained by dissolvingmercury(II) carbonate and oxide in perchloric acid with gentle heating. WhenHg(ClO4)2 solution contacts metallic mercury, the equilibrium
HgðClO4Þ2 þHg"H2O
Hg2ðClO4Þ2 ð5:95Þ
is shifted to the right.
5.4 Organometallic Mercury Compounds
5.4.1 Organometallic Mercury(I) Compounds
Only a limited number of organometallic compounds of mercury(I) are known.Mercury(I) halides and perchlorates form several complexes with weak bases:
2-ethylpyridine, [Hg2(C7H9N)4]X2
4-cyanopyridine, [Hg2L2
0]X2
3-chloropyridine, [Hg2L2
00]X2
4-benzoylpyridine, [Hg2L2
000]X2
where L0 ¼C6H4N2, L00 ¼C6H6NCl, L000 ¼C12H9ON, and X–¼Cl–, Br–, I–,ClO4
–, NO3–.201–203
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The complexes formed by dinitrate and diperchlorate with mercury(I),1,10-phenathroline, [Hg(C12H8N2)2]X2, and 2,20-bipyridyl, [Hg(C10H8N2)2]X2,have been briefly described.204,205 The ability of mercury(I) to form stablecovalent complexes with bases was first demonstrated by Wirth andDavidson.206 In complexes formed by mercury(I) with 4-cyanopyridine and3-chloropyridine, which share the common structure of the complexHg2L2(ClO4)2, the ligands are coordinated via a base nitrogen atom in
approximately the axial position of the dimer Hg2þ2 with weak interaction
between mercury and perchlorate ion.201 This structure is characteristic of allthe complexes of the type.
An important factor for the formation of stable mercury(I) complexes withvarious nitrogen-containing donors is basicity (effective base strength). As itturns out, only ligands with low basicity (based on replaced atoms of pyridinein third and fourth positions) are able to build stable complexes,[Hg2L2](ClO4)2 and [Hg2L4](ClO4)2, whereas the base strength, characteristicof 4-benzylpyridine (pKa 3.35) and pyridine (pKa 5.21), is the critical factor.
201
Hg2(ClO4)2 forms stable bidentate complexes with 1,8-naphthopyridine(pKa 3.36) and 5-nitro-1,10-phenanthroline (pKa 3.55), which have meltingpoints above 673K.201 More basic ligands result in disproportionation ofmercury(I) complexes due to the high affinity of mercury(II) ions towardnitrogen-containing ligand donors. Interesting results were obtained from thereactions between mercury(I) and diphenyltrifluorophosphine, which createscomplexes with the structural formula [Hg–Hg–P(CF3) Ph2]
21 and trifluor-ophosphine [Hg–Hg–PF3]
21.207,208
5.4.2 Organometallic Mercury(II) Compounds
A large number of different metallorganic mercury(II) compounds have beenused for the synthesis of different classes of organic compounds.3,209–211
Organomercury(II) compounds fall into two classes: (a) R2Hg and R0HgRand (b) RHgX, where R and R’ are organic radicals and X–¼Cl–, Br–, I–,ClO4
–, NO3–, SO4
2–, etc. If X–¼Cl–, Br–, I–, CN–, SCN– or OH– ions withpolarized electron shells (soft acids), engaging in covalent bonding withmercury ions, then organomercury(II) compounds with these ions exhibit theproperties of non-polar covalent compounds that have higher solubility inorganic solvents than in water. Organomercury(II) compounds with anionsthat have poorly deformable electron shells (hard bases), such as SO4
2–, CO32–,
PO43–, ClO4
– and NO3–, are salt-like and heteropolar ([RHg]m
1 Xn–).
The solvation energy of organomercuric compounds with covalent bondingis much greater compared with the hydration energy of mercury(II) chlorides,bromides, iodides, etc., which is why they are readily extractible with organicsolvents. Thus, even inert solvents (benzene, toluene) can be used to extractmercury from neutral aqueous solutions.215, 216 Some physical properties oforganic mercury(II) compounds are given in Table 5.17. Additionalthermodynamic data can be found elsewhere.217,218
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The properties of metallorganic mercury compounds depend on the nature ofR radicals. There are three types of compounds. Type one compounds aremercury compounds with aliphatic or aromatic hydrocarbon groups, type twoare mercury compounds with radicals of the type
— C— C —X
where X–¼OH–, Cl–, Br–, etc., and type three are organic halocarboncompounds (CF3, C2F5, C6Cl5).
2,3,209–211 Many known synthesis reactions canbe used to produce organometallic mercury(II) compounds:
(a) Grignard reactions:
RMgX þHgX2 ! RHgXþMgX2 ð5:96Þ
RHgXþRMgX! R2HgþMgX2 ð5:97Þ
(b) Amalgamation reactions:
2RIþNaðHgÞx ! R2Hgþ 2NaI ð5:98Þ
2RIþ CdðHgÞx ! R2Hgþ 2CdI2 ð5:99Þ
2RBrþKðHgÞx ! R2Hgþ 2KI ð5:100Þ
where R¼ alkyl (CnH2n11), vinyl (CnH2n–1) and aryl (C6H5 and benzenederivatives).
(c) Substitution reactions:
RHþHgX2"RHgXþHX ð5:101Þ
C6H6þHgðOCOCH3Þ2 ! C6H6 �HgOCOCH3þCH3COOH ; ð5:102Þ
RMe þHgX2 ! RHgXþMeX ð5:103Þ
RMe þRHgX! R2HgþMeX ð5:104Þ
where Me¼Li, Mg, Al, Tl, Zn, Cd, Pb, etc.(d) Mercurization reactions:
C6H5OCOOHþHg! C6H5HgOCOOH ð5:105Þ
RXþHg! RHgX ð5:106Þ
where X¼Br–, I–, N21 and NHNH2.
(e) Addition reactions:
HC�CHþHgCl2 ! CClH¼CHHgCl ð5:107Þ
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Organomercury(II) compounds RHgX and R2Hg are non-linear. Dialkyland diaryl mercury compounds are highly volatile, toxic, colorless liquids orlow-melting solids. Owing to the low polarity of the C–Hg bond and the lowoxygen affinity, organomercury(II) compounds resist oxygen contained in airand water. However, owing to the poor stability of the C–Hg bond and poorreactivity, organomercury(II) compounds break down when exposed to light,irradiation or heat (thermal decomposition) and produce free radicals. In recentyears, the ability of organomercury(II) compounds to generate free radicals oforganic intermediates has been used to perform various organic syntheses andconstruct organic molecules with predetermined properties.219 The propertiesof free radicals and the methods of their production and application have beenreported.219–222 The properties (spectral characteristics, fluorescence) of theexcited atoms of mercury, their dimers and trimers and various mercurycomplexes with NH3, H2O, H2, rare gases (HgNe, HgAr, HgKr), butylamine,aliphatic alcohols, etc., have been studied.223
Organomercury(II) complexes may serve as a base for the production ofelectrolytes needed to obtain high-purity mercury by electrolytic refining.Organomercury(II) compounds are commonly used to produce a broad class oforganometallic compounds:
ðC6H5Þ2Hgþ 2Na! 2C6H5NaþHg ð5:108Þ
ðC2H5Þ2Hgþ 2Na! 2C2H5NaþHg ð5:109Þ
ðCH3Þ2HgþMg! ðCH3Þ2MgþHg ð5:110Þ
For practical purposes, it is interesting to look at the compounds ofmercury(I) acetate:
Hg2Ac2ðcrystÞ ! Hg2þ2 þAc� ð5:111Þ
with Ks¼ 2.4�10–10, which dissolve in excess sodium acetate and acetic acidthrough the reaction
Hg2Ac2þAc�"H2O
HgAc�3 þHg ð5:112Þ
The solubility of Hg2Ac2(crystal) in water, measured in grams per kilogramH2O, is 100 at 298K and 1000 at 373K. Consecutive acetate complexesformation constants are1,224 K1¼ 3.6�105, K2¼ 2�109, K3¼ 1.9�1013 andK4¼ 1.2�1011.
In oxalate solutions, mercury(II) forms complexes:
Hg2þ2 þ 2C2O2�4 ! Hg2 C2O4ð Þ2�2 ð5:113Þ
with equilibrium constant K¼ 9.2�106. Very valuable properties are offered bymercury(II) ion complexes with glycinate (Gly) ions (HgGly2 K¼ 1.5�1019),ethylenediamine, pyridine, citrate, ethylenediaminetetraacetate (Y4–, HY3–), etc.160
In conclusion, it will be observed that the chemistry of mercury(I) andmercury(II) compounds, which extends to a wide range of reactions, is bothinteresting and intricate and, depending on the nature of the ligands and their
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ratio to mercury, allows one to obtain mercury compounds with differentchemical and physical properties.
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218. D. M. Fairbrother and H. A. Skinner, Trans. Faraday Soc., 1956, 52, 956.219. J. Barluenga and M. Yus, Chem. Rev., 1988, 88, 487.220. V. D. Pokhodenko, A. A. Beloded and V. G. Koshechko,
Oxidation–Reduction Reactions of Free Radicals, Naukova Dumka, Kiev,1977.
221. V. D. Pokhodenko and M. F. Guba, Bull. Ukr. Acad. Sci., 1988, 5, 24.222. D. C. Nonhebel and J. C. Walton, Free-Radical Chemistry, Mir, Moscow,
1977.223. A. B. Callear, Chem. Rev., 1987, 87, 335.224. D. Banerjee and I. P. Singh, Z. Anorg. Allg. Chem., 1964, 331, 225.
Chemical Properties of Mercury 127
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CHAPTER 6
Electrochemical Propertiesof Mercury
6.1 Kinetics and Mechanism of Discharge and Ionization
of Mercury in Simple Electrolytes
Mercury is an ideal electrode material. It exhibits a positive electrode potentialand a high overpotential for releasing hydrogen. It is liquid at roomtemperature and can be easily purified. Therefore, it is a favorable material forthe construction of precise electrode devices with continuously renewedsurfaces of mercury. The fresh mercury surface ensures reproduciblethermodynamic parameters for equilibrium in systems such as Hg/Hg2X2 andHg/HgX2, and also kinetic characteristics of mercury discharge andionization.1–13 The relationship of equilibria in Hg/Hg2X2 (X¼ClO4
�, NO3�,
SO42–) and Hg/HgX2 (X¼Cl�, Br�, I�, CN�, SCN� and others) systems have
been discussed in the literature1–6,11,14–19 and also in Chapter 5. In solutions ofperchloric and nitric acids, the equilibrium in the Hg/HgX2 system:
HgþHgðClO4Þ2ÐHg2ðClO4Þ2 ð6:1Þ
is shifted towards the formation of monovalent mercury ions. The standard
electrode potential of the reduction of Hg2þ2 :
Hg2þ2 þ 2e! 2Hg ð6:2Þ
is E0Hg2þ
2=Hg¼ 0.7960� 0.0005 V (versus NHE)5 in solutions of perchloric acid.
According to Wanderzee and Swanson,6 E0Hg2þ
2=Hg¼ 0.7965� 0.001 V (versus
NHE). A similar value forE0Hg2þ
2=Hg
in the Hg/Hg2(ClO4)2 system was obtained
Mercury Handbook: Chemistry, Applications and Environmental Impact
By Leonid F Kozin and Steve Hansen
r L F Kozin and S C Hansen 2013
Published by the Royal Society of Chemistry, www.rsc.org
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by Choudary and Prasad.11 The potential of the electrode Hg/Hg2(ClO4)2 isdescribed by the relationship
Et¼ 0.80252� 2.51�10�4(T� 273)� 1.0668�10�6(T� 273)2
E0
Hg2þ2=Hg0¼ 0.795578 V in the temperature range 5–35 1C (278–308 K).
Numerous investigators have studied the kinetics and mechanism ofelectrode reactions of mercury(I) in solutions of perchloric acid.1–5,7–10 Thecathodic process of electroreduction of mercury(I) ions consists of two single-electron reactions:
Hg2þ2 þ e �!k1 Hgþ þHg ð6:3Þ
Hgþ þ eÐkk2
ka2
Hg0 ð6:4Þ
that are described by a single kinetic equation:
i¼ kk1 Hg2þ2� �
exp�a1FERT
� �� ka2exp
b1FERT
� �ð6:5Þ
where a and b are transfer coefficients (a1¼ 0.4; b1¼ 1.6) and zl is the numberof electrons at the limiting stage (zl¼ 1). For the proposed kinetic equation, the
order of the cathodic reduction process in eqn (6.2) for Hg2þ2 ions is n¼ 1.
However, upon processing the data collected in the experiments, it was found
that, depending on the current density and concentration of Hg2þ2 ions, the
order of the reactions changes from 2 at high concentrations {[Hg2þ2 ]¼(2.3–5.3)�10�3M} to 0.65 at lower concentrations {[Hg2þ2 ]¼ (1.0–0.59)�10�3M}.
These data demonstrate the complexity of the electrode processes of mercury.Formation of the intermediate ion Hg1 behaves like radicals12 and their mutualinteraction follows the second-order dimerization
Hgþ þHgþ �!kdimerization
Hg2þ2 ð6:6Þ
with a high rate constant, kdimerization¼ (8.0� 1.0)�109 L mol�1 s�1.13 This iswhy this reaction can complicate the course of reaction (6.2).
The kinetics of the electroreduction of Hg2þ2 ions at a mercury electrode in
0.1–1.0M perchloric acid solution were studied using an advanced galva-nostatic double-pulse method7 and also by a quasi-equilibrium method.2,8 Therate of electrode reduction given in eqn (6.2) is described by the current density(current per unit surface area)2 and is given by
g¼ k0 CaC1
C0
� �a
exp � 2aZFRT
� �� C1�a
0 Ca1exp �
2 a� 1ð ÞZFRT
� �� ð6:7Þ
where c0 and ca are the concentration of Hg2þ2 ions in solution and on the
surface of a mercury drop, c1 is the concentration of mercury in the metallicphase, k00 is the rate constant at the standard potential, Z is the overpotential
and a is the transfer coefficient.
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For cathodic electroreduction of Hg2þ2 ions with kinetic control, the current
is given by the equation
i¼4pFa2k00C
1�a0 Ca
1exp �2aZFRT
�1� exp 2ZF
RT
�� �
1þ ak00
2DC1C0
� aexp � 2aZF
RT
� ð6:8Þ
where a is the radius of the mercury drop. The transfer coefficient a and rateconstant k00 are determined by using equation (6.9) for characteristic transfer
time t:
1
t¼
M k00 �2rD
C1�2a0 C2a
1 exp � 4aZFRT
� �1� exp
2ZFRT
� �� �ð6:9Þ
where M is molecular mass, r is density and D is the diffusion coefficient.Table 6.1 gives the transfer coefficients, a, apparent (k00) and standard (k0)
rate constants of electroreduction of Hg2þ2 ions at a mercury electrode in
solutions of perchloric acid, according to Bindra et al.2 Table 6.1 also givesapparent transfer coefficients, a0, which at Z¼ 0 agree well with the value9 ofa¼ 0.40 for a two-step cathodic reaction:
Hg2þ2 þ e! Hgþ2 ð6:10Þ
Hgþ2 þ e! 2Hg0 ð6:11Þ
with z¼ 1 and first-order for Hgþ2 ions.
It should be noted that Hgþ2 ions are reactive and have a short lifetime as they
follow the disproportionation reaction
Hgþ2 þHgþ2 ! Hg2þ2 þ 2Hg ð6:12Þ
at a high rate. The disproportionation reaction rate constant is2kdisproptionation¼ (1.4� 0.2)�1010 L mol�1 s�1.13
The rate of mercury discharge and ionization at a stationary mercuryelectrode is limited by the mass transfer and, takes place with a very lowoverpotential.10 The resulting cathodic reaction follows eqn (6.2), whereas theanodic process is a single-electron reaction:
Hg0 ! Hgþ þ e ð6:13Þ
Table 6.1 Kinetic characteristics of cathodic reduction of Hg2þ2 ions in
solutions of perchloric acid.
Composition of solution A k10 � 102 (cm s�1) k0 (cm s�1) a0 at Z¼ 0
1�10�3 M Hg2þ2 : 1 M HClO4 0.32 2.0 2.37 0.37
1�10�3 M Hg2þ2 : 0.1 M HClO4 0.28 2.5 1.06 0.38
1�10�3 M Hg2þ2 : 0.01 M HClO4 0.34 0.76 1.92 0.37
5�10�4 M Hg2þ2 : 0.1 M HClO4 0.26 1.1 1.11 0.37
5�10�3 M Hg2þ2 : 0.1 M HClO4 0.27 2.2 1.13 0.38
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with the associated dimerization reaction, eqn (6.6), of Hg1 ions. There isvirtually no oxidation of Hg to Hg21 ions at the liquid mercury electrode.
The electrode process of electroreduction of mercury(II) ions is also complex.The standard electrode potential of the reduction reaction
2Hg2þ þ 2e! Hg2þ2 ð6:14Þ
in perchloric acid solution isE0
Hg2þ =Hg2þ2
¼ 0.9119� 0.000314 and 0.913� 0.003V
(versus NHE).15 According to Dobosh,16 the standard electrode potential
E0
Hg2þ =Hg2þ2
¼ 0.920 V (versusNHE). The standard electrode potential for a two-
step reaction:
Hg2þ þ 2e! Hg ð6:15Þ
as was shown in Chapter 5, is E0
Hg2þ =Hg0¼ 0.854 V (versus NHE).17
Taking into account the literature values6,15 for E0
Hg2þ2=Hg0
and E0
Hg2þ =Hg2þ2,
the Luther equation gives E0
Hg2þ =Hg0¼ 0.8547 V (versus NHE). Similar values
of the electrode potentials E0
Hg2þ =Hg2þ2
, E0
Hg2þ2=Hg0
and E0
Hg2þ =Hg0are also
observed in nitric acid solutions.4,16–18 The zero charge potential of mercury is–0.193 V (versus NHE).19 Therefore, the surface of a mercury electrode atapplied potentials is positively charged in simple electrolytes.20–23
Polarization curves for mercury(II) ion reduction and mercury oxidation innitric acid electrolyte on liquid mercury electrodes. In this case, elec-troreduction of mercury ions also takes place at low polarization and isreversible according to eqn (6.14). In the presence of mercury(II) ions, metallicmercury is not formed at moderate polarization since eqn (6.1) reaches equi-
librium very fast. Therefore, Hg2þ2 ions are the only product of elec-
troreduction. Studies of the electroreduction of Hg21 ions in a solutioncomposed of 1MKNO3þ 0.01MHNO3 conducted using polarography,chronopotentiometry and cyclic voltamperometry methods on a gold electrodeestablished that Hg21 ions are reduced reversibly according to eqn (6.14).20 Thecyclic voltamperometric diagram is characterized by one wave. Analysis of thepolarographic diagrams in coordinates log[i/(id – i)2] –E resulted in a straightline with a slope of 0.029V at 298K, which is typical for two-electron processes.It has also been found that with increase in voltamperometric polarization ratethe electrode reaction starts to become irreversible.
Studies of the electroreduction of Hg21 to Hg1 in a 0.1 M solution of HNO3
at a glassy carbon electrode found a single peak that was interpreted as an
integral one and was attributed to the two-step reactions Hg21-Hg2þ2 and
Hg2þ2 -Hg0 of reduction of Hg21 to Hg0 at potentials too close to form two
independent peaks.23
Figure 6.1 shows a voltamperometric curve for electroreduction of Hg21 ionsat a glassy carbon electrode.22 Investigation of the influence of potential sweeprate (n, V s�1) revealed that at nr0.02 V s�1 the electrode process takes place in
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a reversible fashion, whereas an increase in the sweep rate causes kinetic controlof the process (the same as in the study by Torsi and Mamantov20) and atnZ0.4 V s�1 electroreduction of Hg21 ions is irreversible.22 On the other hand,
by taking into account the difference between standard potentials E0
Hg2þ =Hg2þ2
and E0
Hg2þ2=Hg0
, one could anticipate two waves or two distinct peaks. Whether
reaction (6.14) is a single-stage or one-step type, it should be accompanied by achemical reproportionation reaction, eqn (6.16), in the surface layer of themercury electrode:
Hg2þ þHgÐHg2þ2 ð6:16Þ
Voltamperometric studies at a rotating disk electrode made of glassy carbonshowed that the shape of the voltamperometric diagrams depends on whetherthe electrode is coated with mercury or not. If the surface of the electrode is notcovered with mercury, reduction of Hg21 ions is manifested by a singleelongated wave (DEE0.5 V), whereas if it is covered with mercury, two distinctS-shaped waves of different heights are found, as shown in Figure 6.2. Vetter 9
suggested that a cathodic processing treatment of the electrode surface onlypartially covers it with a mercury deposit. Mercury is deposited only on activecenters of the electrode in the form of fine droplets that act as small mercuryelectrodes at the corresponding polarization. Those centers are the locations
ik, μA
Е, V (NHE)
Figure 6.1 Voltamperometric diagram for reduction of Hg21 ions in a solutioncomposed of 0.1 M KNO3þ 0.01 M HNO3 at a glassy carbon electrode.[Hg21]¼ 2.29�10�3 mol; potential sweep rate n¼ 0.02 V s�1.Reproduced with permission from Ref. 22.
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where the reproportionation reaction takes place, generating Hg2þ2 ions. These
Hg2þ2 ions are immediately reduced to Hg0, producing the first reversible S-
shaped wave with a half-wave potential E12¼ 0.427 V (versus SCE). The second
wave with E12¼ 0.297 V (versus SCE) is responsible for reduction of Hg21 to
Hg0 on the bare parts of the electrode surface.We believe that this interpretation of the interesting experimental data is
insufficient since it does not match the electrode potentials of eqns (6.14) and(6.2). The first wave corresponds to eqn (6.14) of electroreduction of Hg21 to
Hg2þ2 , concurrently with the Hg21 ion reproportionation eqn (6.16), and results
in the generation of Hg2þ2 ions. Transformation of Hg21 ions in the course of
reaction (6.16) causes a decrease in the height of wave 1 at E12¼ 0.427 V (versus
SCE). Generation of Hg2þ2 ions according to reaction (6.16) increases the height
of wave 2. Analysis of Figure 6.2 shows that the height of wave 1 decreases by58% due to the consumption of Hg21 ions and the second wave increased bythe same amount.
Taking into account reproportionation, the electrode process can be repre-sented as follows:
3Hg2+ + Hg + 2e → 2Hg22+ + 4e → 4Hg0
1Hg0ð6:17Þ
Different heights of the first and second waves cannot be attributed to
different diffusion coefficients for Hg21 and Hg2þ2 ions. These diffusion co-
efficients, equal to 8.2�10�10 and 9.2�10�10m2 s�1, respectively,24 are fairly close to
ik, μA
Е, V (SCE)
Figure 6.2 Voltamperometric diagrams obtained for reduction of Hg21 at a rotatingdisk-shaped electrode. [Hg21]¼ 2.29�10�3 mol; electrode rotation speedo¼ 1500 rpm. (1) Completely cleaned from traces of metallic mercurydeposits during ionization at E¼ 0.8V (versus SCE) for 5min; (2)electrode partially covered with mercury deposits.Reproduced with permission from Ref. 22.
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each other. In fact, as can be seen in ref. 3, polarographic waves of the elec-
troreduction of Hg21 and Hg2þ2 ions and metallic mercury oxidation, ik, that
corresponds to the reaction Hg21-Hg2þþ
2 , is just slightly greater than ik of the
reaction Hg2þ2 -Hg0. Comparison between the electroreduction of ions Hg21
and Hg2þ2 was first made by Kolthoff and Miller.24
Ref. 3 also demonstrates that the maximum current of mercury ionization inacidic solutions of easy-soluble salts of mercury(I) and -(II) is virtuallyimpossible to reach. This shape of the curves is typical for reversible elec-trochemical reactions.25–28 The results in ref. 3 also show that the discharge andionization in simple electrolytes takes place with very low polarization.According to Bindra et al.,3 potentials of dropping mercury electrodes insolutions of simple salts of mercury(I) and -(II) are defined by the Nernstequations:
E¼E0
Hg2þ2=Hg0þ RT
2Fln Hg2þ2� �
0ð6:18Þ
E¼E0
Hg2þ=Hg0þ RT
2Fln Hg2þ� �
0ð6:19Þ
When Hg2þ2 ions are being reduced, the current is limited by their diffusion to
the electrode and is described by
ik¼ 0:627zFD12 m
23 t
16 Hg2þ2� �
� Hg2þ2� �
0
� ð6:20Þ
while the half-wave potential follows the equation3
E12¼E0
Hg2þ2=Hgþ RT
2Fln
Hg2þ2� �
2
!ð6:21Þ
where z is the number of electrons involved in the electrode reaction, z¼ 2, F isFaraday’s constant, D is the diffusion coefficient of mercury ions, m is the massof the dropping mercury per unit time and t is the dropping time.
According to Geyrovsky and Kuta,3 the equations shown above are alsovalid for the reduction of mercury(II) ions. The mercury(II) ions reactimmediately with metallic Hg on its surface according to eqn (6.16).
The half-wave reduction potentials of mercury(II) ions in non-complexingmedia (ClO4
�, NO3�) on a rotating disk electrode depend on the nature of the
electrode material and the solubility, S, of metallic mercury.23 It was found thatE1
2at an Hg21 concentration of 2�10�4mol L�1 for graphite (SHg¼ 0%),
platinum (SHg¼ 0.090%), gold (SHg¼ 0.136%) and mercury (SHg¼ 100%) is0.060, 0.220, 0.395 and 0.410 V (versus SCE), respectively. It was shown thatsome intermetallics with Hg were formed on the surface of platinum elec-trodes.29 Pt2Hg and PtHg were found at partial coverages (less than amonolayer of Hg) of the platinum electrode surface. PtHg2 formed as a result ofdeposition of two monolayers of mercury. Oxidation of the surface andsubsurface of the intermetallic compounds produces mercury(II) ions, whereas
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the oxidation of volumetric mercury (deposition of more than 50 monolayers ofHg atoms on platinum surfaces) produces only mercury(I) ions.
In sulfuric acid solution (1 M H2SO4), the electroreduction of Hg21 ions wasstudied with the help of a rotating disk electrode with ring and voltammetryusing a linear potential sweep.34 The anodic dissolution of metallic mercury wasstudied with the help of the polarographic method (Na2SO4þH2SO4, NaClO4
up to m¼ 0.1).35 It was established that the rate of the electrode process dependson the potential and, at Eo0.4 V (versus SCE), eqn (6.22) occurs on the glassycarbon electrode:34
2Hg2þ þ 2e! Hg2þ2 ð6:22Þ
whereas at Ek¼ 1.4 V (versus SCE), only Hg2þ2 ion oxidation, the reaction
Hg2þ2 ! 2Hg2þ þ 2e ð6:23Þ
occurs at the ring-disk electrode. The oxidation current at the ring-diskelectrode depends on the electrode preparation conditions. In the course of
iD, μA(a)
(b) iK, μA
ЕD, V (SCE)
ЕD, V (SCE)
Figure 6.3 (a) Polarization i–E curves for electroreduction of 9.9�10�4 M Hg21 in
1 M H2SO4 on a glassy carbon disk electrode and (b) oxidation of Hg2þ2intermediates on a ring electrode, obtained with (1) one pulse on a freshlytreated electrode and (2) two subsequent pulses. Ek¼ 1.48 (versus SCE),n¼ 0.01 V s�1, o¼ 251 rad s�1.Reproduced with kind permission from Elsevier Science r P. Kiekens,R. M. H. Verbeeck, H. Donche and E. Temmerman, Electroanal. Chem.,1983, 147, 235. Ref. 34.
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cathodic polarization of the disk electrode, the current at the ring first increaseswith decreasing disc potential, then drops to zero (see Figure 6.3). This isbecause the formation of Hg(I) ions on the surface of the disc or in the adjacentlayer is limited to the Hg21 ion reduction potential region on the disc. In thecase of a shift of the disk (glassy carbon) electrode potential towards thecathodic region, the electroreduction of Hg21 ions occurs as a one-stepreaction, eqn (6.15), and the electrochemical reaction does not produce anyHg21 ions exhibiting the properties of intermediates. Figure 6.3 shows that,indeed, Hg(I) ions are generated, according to eqn (6.22), on the surface of thedisc at the wave base potentials. However, it will be observed that some amount
of Hg2þ2 ions may also be generated via reproportionation, eqn (6.16). It is also
found that subsequent scanning without reactivation of the electrode surfaceproduces much smaller quantities of Hg(I) ions.
From Figure 6.4, it follows that the ring electrode current, ik, is a function ofthe disk electrode current, iD, at potentials that are more positive than the peakcurrent potential at the ring-disk electrode. The relation between ik and iD isik/iD¼Nexp, where Nexp is the experimental electrode efficiency factor.1 AtEo0.4 V (versus SCE) iD increases, whereas ik decreases; ik/iD decreases andreaches zero at E¼ 0.35 V (versus SCE).
The maximum Hg(I) oxidation current at the ring-disk electrode as afunction of the electrode rotation speed is shown in Figure 6.5.34 The shape of
ik, μA
iD, μA
Figure 6.4 Ring-disk electrode current, ik, as a function of disk-shaped electrodecurrent, iD, of Hg(II) reduction, given potentials that are more positive
than the Hg2þ2 ion oxidation peak potential at the ring; Nexp¼ 0.24, whereNexp¼ ik/iD.Reproduced with kind permission from Elsevier Science r P. Kiekens,R. M. H. Verbeeck, H. Donche and E. Temmerman, Electroanal. Chem.,1983, 147, 235. Ref. 34.
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the ik max–o12 curve is typical for an electrode reaction at a disk electrode, which
is controlled partly by mass transfer and partly by charge transfer at potentialscorresponding to the maximum current at the ring-disk electrode. Thesubsequent beginning of direct reduction of Hg(II) to metallic mercury ispreceded, as seen from Figure 6.3, by the transition of the reaction occurring atthe disk electrode into the diffusion-controlled region (iD¼ constant) atE40.35 V (versus SCE).
Kiekens et al.34 believe that at high iD values, Hg(I) disproportionationaccording to eqn (6.24) is likely to occur:
Hg2þ2 ÐHg0 þHg2þ ð6:24Þ
At potentials that are more negative than 0.4 V and at imax at the ring-diskelectrode, seen in Figure 6.5, direct reduction of mercury(II) to metallic mercury viaeqn (6.15) will gradually replace the single-electrode transfer based on the reaction
Hg2þ þ e! Hgþ ð6:25Þ
Therefore, the electroreduction of mercury(II) ions may be considered as anelectrode process which, depending on electrode potential, occurs via consecu-tive reactions (6.14) and (6.24) and parallel reactions (6.15), (6.25), (6.14) and(6.24). This is why the total number of electrons involved in the cathodic processis non-integral and varies from z¼ 1.65 to 1.85.34 It has been demonstrated thatunder diffusion-controlled conditions, electroreduction of Hg(II) proceeds withtwo electrons (z¼ 2) and ultimately produces the metal. The calculated valueof the Hg(II) diffusion coefficient is (6.9� 0.1)�10�6 cm2 s�1.
ik, max, μA
w1/2, rad-s
–1
Figure 6.5 ik max of oxidation of Hg2þ2 ions at the ring-disk electrode as a function ofrotation speed o
12. [Hg21]¼ 9.9�10�4 M in 1 M H2SO4; Ek¼ 1.4 V (versus
SCE).Reproduced with kind permission from Elsevier Science r P. Kiekens, R.M. H. Verbeeck, H. Donche and E. Temmerman, Electroanal. Chem.,1983, 147, 235. Ref. 34.
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In cases of anodic dissolution of mercury in sulfuric acid solutions underconditions where the solubility product of mercury(I) sulfate (Hg2SO4) cannotbe reached, the function E versus lni should be described by the equation35
E¼E0
Hg2þ2=Hg0þ RT
2FlniA ð6:26Þ
It follows from eqn (6.26) that the anodic current should not depend on theconcentration of sulfate ions. However, experiments35 have shown that anodiccurrent increases with increasing concentration of sulfate ions in the solution,which contradicts eqn (6.26). It follows35 that the anodic current does not reachthe limiting diffusion value, which is observed when a deposit forms on theelectrode surface. The electrochemical behavior of such systems has beenaddressed.36,37
It follows35 that the anodic current is a linear function of the concentrationof sodium sulfate (a), while at the same time the mercury electrode potential isshifted towards less positive values (b). The electrode behavior of mercury isdue to the formation of a complex of mercury(I) with sulfate ions [Hg2SO4]the stability constant of which is 1.5�102 L mol�1.35 The expected values of iAand E for the studied sodium sulfate solutions, obtained with the help of a newnumerical method developed by Kikuchi and Murayama.35 As can be seen,there is a very good correlation between the calculated and experimental valuesfor mercury oxidation currents and mercury electrode potentials in solutionswith different sodium sulfate concentrations.
Table 6.2 gives some kinetic parameters for the electroreduction ofmercury ions in different solutions. It can be seen that the exchange currentsreach high values in non-complexing media. In solutions containing ligandsthat form complex mercury(II) compounds, the exchange currents andconsequently the rate constants become smaller. If inert materials, such asglassy carbon, are used as the electrode material, the exchange current is alsogreatly reduced.
6.2 Kinetics and Mechanism of Discharge and Ionization
of Mercury in Complex-forming Media
Mercury(I) halides, except fluorides, are not dissociated in aqueous solutions,yet, it follows from Chapter 5 that they dissolve in the presence of excess alkalimetal halides and ammonium in solution, producing complex ions HgX�2 and
HgX2�4 . On the whole, mercury(I) compounds are fairly stable in aqueous
solutions and become involved in disproportionation reactions only in thepresence of ligands. Equation (6.27) illustrates a disproportionation reaction ofmercury(I).
Hg2X2 þ zX� Ðkdisproportionation
HgXzþ2� �z�þHg0 ð6:27Þ
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Table 6.2 Rate constants, exchange currents and transfer coefficients during electroreduction of mercury(I) and -(II) ions andmercury oxidation.
Background (mol) Electrode Methoda T (K)
Transfer coefficient
kS (cm s�1) i0 (A cm�2) Ref.a b
Simple electrolytes
(0.59–3.5)�10�3 Hg2þ21 HClO4
Hgliq DPGST 298 (0.3)b 0.7� 0.03 – 16.5� 1.5 31
(0.6–3.4)�10�3 Hg2þ21.0 HClO4
Hgliq DPGST 234.35 (0.3) 0.7� 0.03 – 14� 1.5 31
1.8�10�3 Hg2þ21.0 HClO4
Hgsol DPGST 234.35 (0.3) 0.7� 0.03 – 10� 1 31
(0.59–5.3)�10�3 Hg2þ21.0 HClO4
Hgliq DACPMM 298 0.75 (0.25) Z7.2�10�2 Z5 38
(0.5–2.0)�10�3 Hg2þ21.0 HClO4
Hgliq FR 298 0.86 – B1.5c 0.17–0.69 33
1.0�10�3 Hg2þ20.98 HClO4
Hgliq DPGST 298 0.24 (0.76) 5.2�10�3 0.25 32
3.5�10�4 Hg2þ21.1 HClO4
Hgliq FR 298 0.30 (0.70) 1.4c 5.9y 33
9.9�10�4 Hg2þ21.0 H2SO4
Glassy carbon VDEK 298 0.54–0.60d 0.40–0.44 B10�7d – 34
4.7�10�4 Hg2þ20.2 HClO4
Hgliq FR 296.5� 0.5 0.28 (0.72) 0.36 1.9y 33
(0.02–5.15)�10�3 Hg2þ21 HClO4
Hgliq PRM 298 0.32� 0.02 (0.68� 0.02) 0.019� 0.02 39
2.0�10�3 Hg21
1 HClO4
Hgliq FR 298 (0.53) (0.57) 3.5�10�3 0.68 33
Complex-forming media1�10�5 Hg21, 0.1 CN�
0.9 NaClHgliq PPST 285 0.30� 0.03 0.67� 0.05 3.9�10�5 0.03 40
(0.83–1.04)�10�3 Hg21
4.5 NH4Br, 3.5 HBr (1�10�5–0.5) Hg21Hgliq XP 298 – – 1.5�10�4 42
4.5 NH4Br 3.5 HBr Hgliq DPGST 298 0.5 0.5 47
aDPGST, double-pulse galvanostatic method; DACPM, direct and alternating current polarization method; FR, Faradaic rectification; VDEK, voltammetric;PRM, pulse relaxation method; PPST, pulse potentiostatic method; XP, Chronopotentiometry method.
bExpected transfer coefficients from the relationships aþ b¼ 1 and @lni0 = @ln Hg2þ2� �
¼b = 2.cStandard rate constant.dKinetic parameters of the first step Hg21þ e-Hg1.
Electro
chem
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Therefore, the electrochemical behavior of mercury in simple electrolytes(HClO4, NaClO4, H2SO4, HNO3, etc.) and complex-forming electrolytes (Cl�,Br�, I�, CN�, OH�, SCN�, CH3COO�, etc.) is different on mercury and oninert electrode materials.1–4,7–9,30–44
In the presence of low concentrations of anions (Cl�, Br�, I�) that forminsoluble compounds with mercury(I), the anodic polarization of mercuryelectrodes is manifested by the limiting current and is dependent on theanion concentration and passivation phenomena.1,36,43 The passivation ofmercury anodes is presumably due to a film of poorly soluble salts of univalentmercury, which covers the electrode.45 The passivation of mercury electrodescan be greatly reduced by introducing ammonium ions into the solution.46 Thekinetic regularities of discharge–ionization of mercury in this case are ofconsiderable practical interest. Halide–ammonium electrolytes are used forelectrochemical processes with liquid mercury and amalgam electrodes toproduce high-purity metals. From a theoretical viewpoint, the process ofmercury discharge–ionization in a complex electrolyte with several ligands isvery interesting.
References
1. L. F. Kozin, Electrostatic Precipitation and Dissolution of MultivalentMetals, Naukova Dumka, Kiev, 1989.
2. P. Bindra, A. R. Brown, N. Fleischmann and D. Pletcher, J. Electroanal.Chem., 1975, 58, 39.
3. Ya. Geyrovsky and Ya. Kuta, Basic Polarography, Mir, Moscow,1965.
4. P. Wrona and Z. Galus, in Encyclopedia of Electrochemistry of theElements, ed. A. J. Bard, Marcel Dekker, New York, 1982, vol. 9, pt. A,pp. 1–227.
5. S. E. S. Wakkad and T. M. Salem, J. Phys. Chem., 1950, 54, 1371.6. C. E. Wanderzee and J. A. Swanson, J. Chem. Thermodyn., 1974,
6, 827.7. M. Kogoma, T. Nakayama and S. Aoyaqui, J. Electroanal. Chem., 1972,
34, 123.8. P. Bindra, A. P. Brown and M. Fleischmann, J. Electroanal. Chem., 1975,
58, 31.9. K. J. Vetter, Electrochemical Kinetics; Theoretical and Experimental
Aspects, Academic Press, New York.10. L. F. Kozin, N. I. Ivanchenko and A. A. Nikitin, Zhn. Prikl. Khim., 1982,
55, 1001.11. C. K. Choudary and B. Prasad, J. Indian Chem. Soc., 1982, 59, 555.12. R. S. Eachus, M. C. R. Symons and J. K. Yandell, Chem. Commun., 1969,
17, 979.
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13. M. Farraggi and A. Amozig, Int. J. Radiat. Phys. Chem., 1972, 4,353.
14. S. Papoff, J. A. Riddick, V. I. Wirth and L. D. Orgh, J. Am. Chem. Soc.,1931, 53, 1195.
15. S. R. Carter and R. Robinson, J. Chem. Soc., 1972, 1, 267.16. D. Dobosh, Electrochemical Constants, Mir, Moscow, 1980.17. V. M. Latimer, The Oxidation States of the Elements and Their Potentials in
Aqueous Solutions, Izd-vo Inostr. Lit., Moscow, 1954.18. S. Hietanen and L. G. Sillen, Ark. Kemi, 1956, 10, 103.19. E. I. Hrusheva and V. E. Kazarinov, Electrochemistry, 1986, 22,
1262.20. G. Torsi and G. Mamantov, J. Electroanal. Chem., 1971, 32, 465.21. M. S. Shuman, Anal. Chem., 1969, 41, 142.22. R. G. Dhaneshwar and A. V. Kulkarni, J. Electroanal. Chem., 1979,
99(2), 207.23. M. Stulikova, J. Electroanal. Chem., 1973, 48, 33.24. I. M. Kolthoff and C. S. Miller, J. Am. Chem. Soc., 1941, 63, 2732.25. K. P. Butin, R. D. Rackimov and I. V. Novikova, Vestnik MGU, Ser. 2,
1990, 31, 574.26. A. G. Stromberg, Zh. Fiz. Khim., 1953, 27, 1287.27. A. G. Stromberg, Zh. Fiz. Khim., 1955, 29, 409.28. A. G. Stromberg, Zh. Fiz. Khim., 1955, 29, 2152.29. M. Z. Hassan, D. F. Untereker and S. Bruckenstein, J. Electroanal. Chem.,
1973, 42, 161.30. R. Tammamushi, Kinetic Parameters of Electrode Reactions of Metallic
Compounds, Butterworths, London, 1975.31. H. Gerisher and M. Krause, Z. Phys. Chem., 1958, 14, 184.32. H. Matsuda, S. Oka and P. Delahay, J. Am. Chem. Soc., 1959, 81,
5077.33. H. Imai and P. Delahay, J. Phys. Chem., 1962, 66, 1108.34. P. Kiekens, R. M. H. Verbeeck, H. Donche and E. Temmerman, Elec-
troanal. Chem., 1983, 147, 235.35. K. Kikuchi and T. Murayama, Bull. Chem. Soc. Jpn., 1988, 61,
4269.36. L. F. Kozin, Physico-Chemical Basics of Amalgam Metallurgy, Nauka,
Alma-Ata, 1964.37. K. Kikuchi and T. Murayama, Bull. Chem. Soc. Jpn., 1988, 61, 3159.38. H. Gerisher, Z. Elektrochem., 1951, 55, 98.39. W. D. Weir and C. G. Enke, J. Phys. Chem., 1967, 71, 280.40. M. Perez-Fernandez and H. Gerisher, J. Phys. Chem., 1960, 64, 477.41. N. Tanaka and T. Murayama, Z. Phys. Chem. (Frankfurt), 1959, 21,
146.42. N. Tanaka and T. Murayama, Z. Phys. Chem. (Frankfurt), 1958, 14,
370.43. L. F. Kozin and Ya. P. Suchkov, Ukr. Khim. Zh., 1991, 57, 612.
Electrochemical Properties of Mercury 141
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44. J. Schwade and A. Chon Dien, Electrochim. Acta, 1962, 7, 1.45. M. T. Kozlovskii, A. I. Zebreva and B. P. Gladyshev, Amalgams and Their
Application, Nauka, Alma-Ata, 1971, pp. 81–82.46. L. F. Kozin and A. A. Nikitin, Izv. Akad. Nauk Kazakh., Ser. Khim., 1970,
1, 36.47. L. F. Kozin, Ukr. Khim. Zh., 1991, 57, 585.
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CHAPTER 7
Lighting
7.1 Introduction
Mercury plays an extremely important role in discharge lighting. It is used as alight source and as a buffer gas to carry current through a discharge. Manytypes of discharge light sources contain mercury, including fluorescent, high-pressure mercury, ultra-high-performance (UHP) mercury, high-pressuresodium and metal halide lamps. Numerous monographs1–4 have been devotedto the physics of lamp discharge and operation, so only a very brief explanationof the mechanism of the emission of light is given here. The emphasis is on therole of mercury in the discharge and mercury-containing materials used in theselamps. Mercury is the essential element necessary for producing light influorescent, high-pressure mercury and UHP lamps. Mercury is used in otherlamp types in conjunction with other metals or metal halides. Mercury(II)iodide is added to some lamps.
Fluorescent lamps involve low-pressure discharges and may be classified ascompact, linear, cold cathode or germicidal. High-pressure and UHP (i.e.,ultra-high-pressure) lamps contain mercury at pressures from a few to severalhundred atmospheres and emit light in the ultraviolet, visible and infraredregions. High-pressure sodium lamps contain a binary Na–Hg or a multi-component amalgam. Sodium radiation is the dominant emission in thesedischarges. Metal halide lamps may contain mercury or may be mercury free.Metal halide lamps may contain an assortment of halides in addition tomercury or a mercury replacement such as zinc iodide. The metal halides emitimportant spectral lines and contribute substantially to the efficiency ofconverting electrical energy to light and to the quality of the emitted light.
The science of quantifying light quality is a complex subject. Althoughdiscussions of the topics involved in light source quality have been reported,5
Mercury Handbook: Chemistry, Applications and Environmental Impact
By Leonid F Kozin and Steve Hansen
r L F Kozin and S C Hansen 2013
Published by the Royal Society of Chemistry, www.rsc.org
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several key parameters are used to describe light quality and lamp operatingtemperature. These include the color rendering index (CRI) and the correlatedcolor temperature (CCT). Typical mercury contents, lamp performances andlight quality measures, namely CRI, CCT and efficacy, found in dischargelighting applications, according to lamp type, are given in Table 7.1.
7.1.1 Lamp Color and Quality Measurements
A measure of a lamp’s color quality is defined as the color rendition index(CRI). CRI is defined on a scale from 0 and 100, where the CRI for sunlightand a halogen lamp is defined as 100. The correlated color temperature (CCT)is the measure used to describe the relative color appearance of a white lightsource. The CCT of a light source is the color temperature of a Planckian(black-body) radiator that best approximates it and indicates whether a lightsource appears more yellow/gold/orange or more blue, in terms of the range ofavailable shades of ‘white.’ CCT is given in kelvin. A CCT of 2700K is ‘warm’and 5000K is ‘cool.’6 CCTs over 6000K are bluish white in color whereasCCTs around 2700K appear slightly yellowish and are typical colortemperatures of an incandescent lamp. Halogen lamps have a CCT of about3000K and sunlight about 5000– 6500K.
7.2 Fluorescent Lighting
Fluorescent lamps contain a small mercury dose that emits UV radiation at185.0 and 253.7 nm. The UV radiation is converted into visible light by aphosphor. The ideal mercury vapor pressure in a fluorescent lamp is 0.8 Pa(6 mTorr) and, for pure mercury, occurs close to 40 1C (313K). Only around50 mg of the mercury dose is in the discharge as a vapor during operation.10 Itshould be mentioned that an auxiliary or buffer gas is also necessary for theoperation of fluorescent lamps. An optimum pressure for an auxiliary gas suchas argon is between 200 and 300 Pa.11 A schematic showing the operation offluorescent lamps is shown in Figure 7.1.
Table 7.1 Mercury contents in different discharge light sources.7–9
Lamp typeMercury contentrange (mg) Efficacy (lm W–1) CCT (K) CRI
Mercury vapor 25–225 40–60Ultra-high-pressure 2.5–10 60–75 7000–8000 57High-pressure sodium 20–145 100–120 2200–2700 20–70Quartz metal halidea 2.5–225 60–120 2700–6500 50–95Ceramic metal halide 2.5–30 60–120 2700–6500 70–95T-5 linear fluorescent 1–3 61–100 4000–5000 62Compact fluorescent 1–3 61–100 4000–5000 62
a May be higher for very high wattage lamps.
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Fluorescent lamp operation consists of the following steps:
1. Power through the electrodes heats them and gives off electrons (theelectrodes are covered with an emission mix that assists in extractingelectrons).
2. The electrons excite mercury atoms.3. The mercury atoms fluoresce and create UV radiation (185 and 254 nm).4. The phosphorescent wall coating converts UV into visible light.
The spectrum of a commercial fluorescent lamp is given in Figure 7.2. Thelumen output of fluorescent lamps is strongly dependent on the mercury vaporpressure, and the latter is strongly dependent on the temperature, as described
Figure 7.1 Schematic illustration of a fluorescent lamp. Courtesy of Philips Lighting.
Figure 7.2 Spectrum of a high-CRI fluorescent lamp.Reproduced from Ref. 12.
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in Chapter 1. At low temperatures, too few mercury atoms are present in thegas phase and a fluorescent lamp will have a sub-optimum efficacy. Attemperatures above the optimum pressure, mercury atoms will be abundant inthe gas and self-absorption of UV radiation will occur.
The luminous efficacy of fluorescent lamps has improved greatly since theywere first introduced in 1938. Not only have phosphors improved greatly andcontributed to the increased efficiency, but also the use of krypton or xenon asthe fill gas and the recent use of high-frequency operation have enabledfluorescent lamps to become very efficient light sources. At the same time,mercury has been more accurately dosed into fluorescent lamps by the use ofamalgams, glass capsules and other devices.
7.2.1 Mercury Content in Fluorescent Lamps
The mercury vapor required in the gas phase for maximum light output at theoperating temperature is small relative to a typical mercury dose. For example,a typical 4 ft T8 lamp requires only about 50 mg of Hg and a 15 W CFL requiresonly about 10 mg. Mercury consumption over the life of the lamp demands thatmuch larger doses are used. The relative importance of these consumptionreactions is shown in Table 7.2.13
Successful approaches that permit mercury reduction due to consumptioninclude coatings on the glass bulb wall, coatings on the phosphor particles,additives to the phosphor layer14,15 and coatings on top of the phosphor layer.Materials used in coatings as barriers to mercury consumption reactionsinclude Al2O3, Y2O3 and other metal oxides in both particulate and vitreousforms. Industry has made substantial progress in reducing the mercury contentin fluorescent lamps over the last 30 years. The reduction in mercury dosed intofluorescent lamps is provided in Table 7.3 for the 4 ft linear lamp types.16
7.2.2 Amalgam-controlled Mercury Vapor Pressure
Amalgams have one of two purposes in fluorescent lamps: one is to regulate themercury vapor pressure and the other is to make handling and dosing mercurysafer and more accurate than handling liquid mercury. Mercury vapor pressurecontrol, i.e., regulation, of the mercury vapor pressure over a wide temperaturerange, generally between 60 and 140 1C, is required in fluorescent lampsoperating in outer jackets or in enclosed fixtures and in high-power germicidal
Table 7.2 Mercury consumption mechanisms.13
Componentconsuming Hg Factor affecting consumption
Relativeimportance
Glass without coating Glass type, wall loading, phosphorproperties
High
Phosphor layer Phosphor type, grain size, additives Medium to lowEmission material Cathode shield, electrical factors Medium to lowGlass stems Glass type Low
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lamps with high lamp wall temperatures. Various amalgams have been used toregulate mercury vapor pressure, two of the most successful beingPb–Bi–Sn–Hg and Bi–In–Hg. The use of Pb–Bi–Sn–Hg has been steadilydeclining because of its lead content. However, its main advantage is itsrelatively low cost compared with Bi–In–Hg. Indium metal is significantly moreexpensive then either bismuth or tin.
Bi–In–Hg amalgams were reported in 1977.17 Early compositions ofBi–In–Hg amalgams contained between about 3 and 12 wt% of mercury and20–30wt% of indium. Indium dramatically reduced the mercury vaporpressure of these amalgams between about 50 and 140 1C. Recently, Hein andRaiser18 and Hellebreker and Kaldenhoven19 suggested the use ofBi–Sn–In–Hg (where the indium content is between 3 and 5 wt%) as a lowerindium modification of Bi–In–Hg. Vapor pressure curves for these amalgamsare shown in Figure 7.3.
Many other amalgams have been developed to regulate the mercury vaporpressure in a fluorescent lamp. Examples of amalgams regulating the mercuryvapor pressure are given in Table 7.4.
7.2.3 Temperature-controlled Amalgams
Temperature-controlled amalgams have no significant effect on the vaporpressure of mercury. They only provide a mechanism for administering(dosing) lamps with a precise quantity of mercury.
7.2.3.1 Zn–Hg Amalgams
Zinc–mercury amalgams27 were introduced as a means of delivering a solidmercury dose into a fluorescent lamp. The shape of the equilibrium phasediagram28,29 (Figure 7.4) favors a high mercury vapor pressure at roomtemperature. When the mercury vapor pressure above a mercury–zinc pellet
Table 7.3 Mercury dose per lamp in 4 ftlinear fluorescent lamps using thebest available technology.
Yearmg Hg (using bestavailable technology)
1984 641986 431988 401990 331992 331994 331996 161998 102000 52006 4
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containing 50 wt% Hg was measured,30 its vapor pressure was found to beabout 95% of the vapor pressure of pure mercury at temperatures wellabove the peritectic point. The surprisingly high vapor pressure was explainedby the presence of a metastable mercury-rich liquid in the manufacturedproduct.27
The mercury vapor pressure over the temperature range 5–70 1C is expressedby the equation
logðpZn�Hg; PaÞ¼ �3214
Tþ 7:293 ð7:1Þ
Zinc is used only as a carrier to hold mercury until it can be released insidea fluorescent lamp. The mercury vapor pressure above a equimolar Zn-Hgamalgam is given in ref. 30. As indicated by the phase diagram, the g phase isreported to melt at 42.9 1C. However, in actual tests by differential scanningcalorimetry, alloys of predominantly g phase melt at 65–75 1C.
3
3
1
1
2
2
Figure 7.3 Vapor pressure of Bi–Sn–In–Hg amalgams.18 Compositions (wt%): 1, 58Bi–38 Sn–3 In–0.7 Hg; 2, 57 Bi–37 Sn–5.5 In–1.2 Hg; 3, 58 Bi–37 Sn–4In–1 Hg.Reproduced from Ref. 18.
Table 7.4 Regulating amalgams used in fluorescent lamps.
Amalgam Ref.
In–Hg 20In–Sn–Hg 21Pb–Bi–In–Hg 22Bi–In–Hg 23Pb–Bi–Sn–Hg 24Pb–Bi–Ag–Hg 25In–Sn–Zn–Hg 26
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7.2.3.2 Sn–Hg Amalgams
Sn–Hg amalgams also exhibit a high mercury vapor pressure at roomtemperature. Although measurements of the mercury vapor pressure aboveliquid Sn–Hg are plentiful, vapor pressure measurements above the solid aremore scarce.31 Vapor pressure measurements of an Sn–Hg amalgam are givenin and replace with ref. 31.
Sn–Hg amalgams have been known almost since antiquity and are a keycomponent of dental amalgam. A thermodynamic assessment of the Sn–Hgphase diagram32 is shown in Figure 7.5. Sn–Hg amalgams are useful in fluor-escent lighting applications because they can have mercury contents betweenabout 10 and 50 wt%.33
7.2.4 Mercury Dispensers
7.2.4.1 Bi–Sn–Hg Amalgams
Bismuth–tin–mercury amalgams have been employed as a method toreduce mercury vapor pressure, similarly to Bi–In–Hg, and as a mercurydispenser for cold cathode fluorescent lamps.37 A thermodynamic model of theBi–Sn–Hg phase diagram has been calculated based on experimental data.38–42
Figure 7.6 gives the calculated liquidus projection. It predicts the
Figure 7.4 Zn–Hg equilibrium phase diagram.Reproduced with kind permission from ASM International.28
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Hg Weight Fraction Sn Sn
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Tem
pera
ture
/°C
250
200
150
100
50
0
–50
–100
Liquid
γ
β
δ
HgSn4
α-Sn
β-Sn
(Hg)
Figure 7.5 Calculated Sn–Hg phase diagram. The b-phase has been simplified to astoichiometric compound (HgSn38).Reproduced with kind permission from Springer ScienceþBusinessMedia.32
Bi
Sn
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
Hg
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0 240 °C200 °C160 °C120 °C80 °C
(Bi)
β-Sn
γ
HgSn38 ( (β))
δ
40 °C
Mol
e Fr
actio
n Hg
Mole Fraction Sn
Figure 7.6 Calculated Bi–Sn–Hg liquidus projection.44 Courtesy of APL EngineeredMaterials, Inc.
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decomposition of the b-phase (HgSn38) from the binary Sn–Hg phase diagraminto g- and b-Sn. The vapor pressure above one composition of Bi–Sn–Hg hasbeen measured.43
7.2.4.2 Ti–Hg Amalgams
Intermetallic compounds composed of titanium and mercury were developed tointroduce mercury into fluorescent lamps.34–36 The amalgams operate byreleasing mercury at very high temperatures from the compounds Ti3Hg andZr3Hg. Della Porta and Rebaudo34,35 reported the synthesis of g-Ti3Hg. Finetitanium powder passing through a 400-mesh screen is placed in a crucible withmercury and heated at about 800 1C for 3 h. The resulting alloy consistsessentially of g-Ti3Hg. Zirconium may also be used to form a zirconium–mercury amalgam.36
7.3 Measurement of Mercury Vapor Pressure of
Fluorescent Lamp Amalgams
Several methods are available for quantifying the temperature dependenceof the mercury vapor pressure in the region of operation of fluorescentlamps. These methods include direct static measurement, atomic absorptionspectrometry (AAS) and Knudsen effusion mass spectrometry. Amalgamvapor pressures at room temperature are fairly low and require relativelysophisticated equipment and careful experimental work to be measuredcorrectly.
7.3.1 Vapor Pressure Measurement System
The vapor pressure measurement system (VPMS) is a static measurement.45–47
Total degassing of the sample and the apparatus is a prerequisite for a staticmeasurement of its vapor pressure. The pressure is measured by a capacitancediaphragm absolute gauge. Calibration of the capacitance diaphragm absolutegauge is performed at equally spaced pressures from 0 to 1300 Pa. The sample isimmersed in a constant-temperature bath that allows adjustment of the sampletemperature. Temperatures in the range from 223 K (–50 1C) to about 400 K(127 1C) are generally possible. The sensor temperature is kept constant andconstrains the upper temperature limit of the vapor pressure measurement to5 K below the sensor temperature.
The vapor pressure of the Zn–Hg amalgam discussed in Section 7.2.3.1 wasmeasured by the VPMS while decreasing the temperature from 70 to 40 1C.48
The vapor pressure of Zn–Hg obtained during the descending temperatureprofile is expressed by the equation
logðp;PaÞ¼ �3202:4T
þ 10:143 ð7:2Þ
and was in excellent agreement with AAS measurements.30
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7.3.2 Atomic Absorption Spectrometry
AAS can be used to measure the vapor pressure of a fluorescent lampamalgam.17,30 The 254 nm radiation from mercury is used to measure theabsorbance of mercury vapor from an amalgam. Measurement temperaturesare limited by the dimensions of the absorption cell. The quartz absorption cellmust be at a higher temperature than the sample to prevent condensation ofmercury vapor on the window and it must be aligned by minimizing theabsorbance reading. Absorbance (A) readings of the mercury vapor in the cellare typically recorded to a precision of � 0.0001 absorbance units (� 0.001absorbance units above A¼ 1.000) as the temperature is increased.30 The zeroabsorbance value can be checked with the cell removed from the path.Absorbance readings may be converted into pressure by use of mercury as astandard.
7.3.3 Knudsen Effusion Mass Spectrometry
Measurement of the vapor pressure of pure mercury by AAS at temperaturesabove 80 1C is difficult owing to high absorbance values. One means of over-coming this obstacle is to use Knudsen effusion mass spectrometry (KEMS).Vapor pressure measurements at temperatures up to 200–300 1C were madeby Hilpert on a specially designed Knudsen effusion system.49–53 An advantageof the KEMS method is the measurement of all gaseous species. Hilpertmeasured the vapor pressure of magnesium and calcium amalgams in a KEMSsystem.
A quadrupole mass filter and Knudsen cell operating under high vacuumwere used. A pressure of 10–5 Pa in the effusion orifice corresponds to a pressuresmaller than 10–9 Pa in the ion source. Two orifice diameters were used in themeasurement of the vapor pressures of MgHg and MgHg2. The following least-squares equations were obtained for Hg vapor pressures:
logðpMgHg;PaÞ¼ �ð4845:0 � 43:1Þ =T þ ð9:882 � 0:092Þ ð7:3Þ
logðpMgHg2 ;PaÞ¼ �ð3400:7 � 31:6Þ =T þ ð10:087 � 0:045Þ ð7:4Þ
7.4 High-pressure Mercury Lamp
The high-pressure mercury discharge lamp has been extensively discussed byElenbaas.4 A continuous transition from a low- to a high-pressure dischargeoccurs in a mercury discharge. The luminous efficacy exhibits a maximum for agiven tube diameter and current at the pressure used for fluorescent lampoperation. As pressure is increased, the luminous efficacy passes through aminimum before it begins to increase with increasing pressure. The high-pressure mercury arc operates at a pressure of between 2 and 5 atm.
The core of the high-pressure mercury arc itself operates at a temperaturebetween 5000 and 7000 K. Some of the important spectral lines of mercury inthe discharge are l¼ 491.6, 546.1, 577.0, 579.0 and 643.8 nm.
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7.5 Ultra-high-performance Lamps
Ultra-high performance (UHP) lamps are ultra-high-pressure mercury lampsused commercially in video and projection applications. UHP lamps contain upto 10 mg of mercury and operate at pressures of B20–30 MPa (B200–300atm). These lamps produce a luminous efficacy of about 60 lmW–1. Theirelectrode gap is very short, typically on the order of 1.0–1.3mm.3 Anapproximately 2 mm thick quartz envelope is used to contain the extraordinarypressures obtained in UHP lamps. The coldest point on the quartz envelope(the cold spot temperature) must be above 1100 K (823 1C) to evaporatecompletely all of the mercury in the arc tube. A schematic of the arc tube isshown in Figure 7.7.
The spectrum of UHP lamps is comprised of atomic emission from mercury,molecular emission from the Hg2 dimer and electron-atom bremsstrahlungradiation. The 185 and 253.7 nm resonance lines of mercury (both UV lines) aretotally absorbed within the plasma.3 The mercury plasma exhibits a highelectrical resistance that results in high operational voltages and large powerdissipation into a very small volume. The spectrum of a UHP is shown inFigure 7.8.
7
4
5
3
1
26
Figure 7.7 Schematic diagram of a 50 W UHP lamp54 operating at B200 bar. TheCCT is between 7000 and 8000 K, the Hg content is 6mg, the wall loadingis 130Wcm–2, the luminous efficacy is 58 lmW–1 and the electrode gap is1.2mm. 1, Lamp; 2, elliptical lamp envelope; 3, cylindrical quartz parts; 4,molybdenum foil; 5, electrodes; 6, electrode coils; 7, current supply wires.Reproduced from Ref. 54.
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7.6 High-pressure Sodium Lamps
High-pressure sodium (HPS) discharge lamps are highly efficient lightsources.1,55 High-pressure sodium lamps are characterized by a long service lifeof 20 000 h or more2,56 and are capable of providing a maximum luminousefficacy of 100–120 lm W–1.
Sodium amalgams, i.e., sodium and mercury alloys, are used as the light-emitting media in these lamps. Spheres of sodium amalgam57,58 are obtainedfrom high-purity sodium and mercury but may also contain a third elementsuch as thallium, indium or cesium to improve color rendition. A typical high-pressure sodium lamp design is shown in ref. 1.
The arc tube is mounted in an external vacuum outer jacket. A dose of B25mg of sodium amalgam is placed into a 400 W lamp discharge tube and xenonis injected until its pressure reaches (2.4–2.7) �103 Pa. Lamps of lower powerreceive smaller amounts of amalgam.
A special high-voltage pulse starts a discharge in the xenon gas and leads toevaporation of mercury and sodium. Mercury vapor acts as a buffer gas. Theionization potential of sodium is Eu
Na¼ 5.14 eV, the excitation potential and the
deepest light emission levels of sodium, EbNa¼ 2.09 eV, are significantly smaller
than those of mercury: EuHg¼10.39 eV; Eb
Hg¼ 4.89 and 6.71 eV at the principal
quantum number of n¼ 6 of the outer shell of an excited mercury atom.59 Sincethe sodium ionization and excitation potentials are considerably smaller thanthose of mercury, most atoms of sodium in the vapor are ionized and radiatelight. Owing to their high excitation potential, the atoms of mercury arevirtually not involved in the emission, even under considerably higher pressure.Therefore, the vapor of mercury controls the lamp current and power.
In effect, only atoms of sodium in the gaseous phase are responsible for lightand color parameters of the high-pressure lamps. The main excitation levels of
Figure 7.8 Spectra of a 120 W UHP lamp at different mercury pressures. The lamphas an arc gap of 1 mm. The 290 bar spectrum has the highest continuumradiation and the lowest overall peak heights.Reproduced with permission from Ref. 8.
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sodium atoms are shown in ref. 1 and 60. Broadened resonance lines ofsodium (l¼ 589.59 and 589.99 nm) are responsible for the yellow–orange coloremitted by HPS lamps.59 Spectra from a high-pressure sodium lamp are shownin ref. 3.
HPS lamps with a color rendering index of about 302,56 are not used forindoor illumination where high CRI is necessary. This is why improvement ofthe spectral distribution of the emitted light is of critical importance for manyresearchers. It has been found that the addition of lithium, thallium or indiumto mercury lamps causes emission of red (l¼ 671 nm), green (l¼ 535 nm), blue(l¼ 451 nm) and violet (l¼ 410 nm) light.59 It is possible to obtain a continuumspectrum similar to that of white light (daylight) using additives to sodiumamalgam. Some physicochemical and spectral properties of mercury andsodium and also some promising additives2,61–65 for improved color renderingand other parameters of HPS lamps are given in Table 7.5.
Thorough studies of the discharge physics of sodium atoms demonstratedthat by altering the sodium vapor pressure it is possible to control the dischargeparameters and improve color rendering.66 It has been found that themaximum luminous efficacy is reached at a sodium vapor pressure of 2.7�103to 2.7�104 Pa (20–200 Torr of mercury).2,56,59–62,67 The discharge temperaturein a 400 W HPS lamp is 2300–2770 K depending on the specifics of the lampdesign. The cold spot temperature of the discharge tube is about 930–970 K.Thermal properties of sodium amalgams in a broad range of temperatures havebeen studied.68–73
Data analysis shows that negative deviations from an ideal solution areobserved even at high temperatures, although the deviation from ideality
Table 7.5 Physicochemical and spectral characteristics of variouselements.2,61–65
ElementaTmelt
(K)Tevap
(K)
Ionizationpotential(eV)
Excitationpotential(eV)
Characteristicradiationwavelength(nm)
Vaporpressure,(Pa)(T¼ 900 K)
Sodium (3) 371 1151.2 5.14 2.10 589.59 5.07�103588.99
Mercury (6) 234.32 629.81 10.43 4.89 253.05 1.05�1086.71 184.95
Thallium (6) 577 1748 6.11 3.74 535.05 2.41377.57
Indium (5) 429.78 2297 5.78 3.02 451.13 3.07�10–3410.18
Potassium (4) 336.4 1032 4.34 1.61 769.90 2.43�1041.62 764.49
Rubidium (5) 312.7 959.2 4.18 1.56 794.76 5.40�1041.59 780.03
Cesium (6) 301.6 943 3.89 1.39 894.35 6.55�1041.45 852.11
a Values in parentheses are the principal quantum numbers for the outer shells of excited atoms.
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becomes smaller with increase in temperature. The composition of sodiumamalgam commonly used in HPS lamps is 78–85 at.% sodium and 15–22 at.%mercury.2,61,62,66,67,73
Sodium vapor pressures56,60,67,71,73 may be calculated under conditionssimilar to the operating conditions of an HPS lamp from thermodynamic datafor the Na–Hg system.
Various metals are added to sodium amalgam to improve the color renditionand enhance the sodium vapor pressure in HPS lamps.67,73–76 Thethermodynamic properties of ternary amalgam systems Na–Me–Hg, whereMe¼ In, Tl, Cs or Rb, have been studied.59,73,74,77–82
Values of sodium activity in the sodium–mercury binary system. Componentactivities in the sodium–thallium–mercury ternary system for the three T–cplanes of the Gibbs triangle are given in ref. 55. It can be seen that both thesodium and mercury activities exhibit negative deviations from ideal solutionsat virtually all concentrations, whereas the thallium activity at certainconcentrations shows positive deviations. Apparently, the sodium activity inthe ternary sodium–thallium–mercury system is higher than that in the binarysodium–mercury system. This is responsible for an increase in the vaporpressure in the Na–Tl–Hg system. The pressures of sodium and mercury vaporare higher in the ternary than in the binary system. This pattern also holds forthe sodium vapor pressure at 873–973 K.55 The vapor pressure increase isfavorable for application of sodium–thallium amalgams in HPS lamps.
The activity of sodium in the sodium–indium–mercury system at 733 K isknown. The pressures are lower than the pressure of sodium above asodium–mercury melt at 773 K based on calculations71 and shown in Table 7.6.A temperature increase from 873 to 973 K has virtually no effect on the sodiumvapor pressure. It should be noted that there is a close relation between thepressure of sodium and mercury vapors in the discharge tube, voltage appliedto the lamp, light intensity and patterns of the sodium discharge lines.
To determine possible combinations of thallium and indium in ternaryamalgams, Dergacheva et al.74 studied the electrical and spectral characteristicsof HPS lamps with various media in the discharge tube. Table 7.6 gives theelectrical and spectral characteristics of lamps with thallium and indium doses
Table 7.6 Electrical and light characteristics of HPS lamps with Tl and Inadded to the discharge.74
AmalgamComposition(at.%)
Voltage(V)
Current(A cm–2)
Power(W)
Light flux(lm)
Luminousefficacy(lm W–1)
Na–Hg 78–22 120 4.9 400 40 000 100Na–Tl–Hg 50–25–25 136 3.7 420 41 320 98Na–Tl–Hg 40–12–48 130 3.0 373 32 220 86Na–Tl–Hg 20–16–64 107 4.5 390 19 990 50Na–In–Hg 12–48–40 100 2.6 310 13 950 45Na–In–Hg 8–32–60 105 2.5 270 10 780 40Na–Tl–In–Hg 63–7–13–17 103 4.6 375 38 070 101
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in the discharge tube in the form of three- and four-component amalgams.The changes in the lamp current and power are insignificant. The light flux andefficiency are very sensitive to the sodium content since a decrease in Na contentreduces the sodium vapor pressure.
Decreases in the sodium concentration in a ternary amalgam from 50 to 20at.% reduce the luminous efficacy by almost half. For the same reason, lowlight flux and low luminous efficacy are observed in lamps with high concen-trations of indium (see Table 7.6). Use of a quaternary amalgam as the emissionsource with the sum of thallium and indium no greater than 20–25 at.% andsodium content no less than 50 at.% makes it possible to develop lamps withsufficiently high light flux and efficiency. The drawbacks of sodium lamps withadditions of other components, e.g., with a quaternary amalgam, are moredifficult ignition and complications with stabilization of parameters. Increasingthe indium and thallium content in the amalgam by more than 25 at.% causeHPS lamps to ignite and operate in a stable fashion only at 380 V.
Of all compositions surveyed, the best results were obtained with Na–Tl–Hg(50:25:25 at.%). A series of lamps filled with this composition demonstratedstable characteristics after 100 h of operation. Introduction of thallium in thesodium–mercury discharge causes pronounced changes in the emissionspectrum. Thallium lines and broadened sodium lines appear. A faint peak atl¼ 451 nm has been noted in the spectra of lamps containing indium. Thissmall peak at 451 nm has almost no impact on the light radiation power in theblue region. The CCT change caused by introduction of thallium in thedischarge process is demonstrated in Table 7.7.
Cesium is often added to sodium mercury amalgams. A detailed discussion ofthe effects of cesium on high-pressure sodium discharges is can be foundelsewhere.55 Light and electrical characteristics of Na–Cs–Hg lamps are givenin Table 7.8. A high-CRI lamp was reported by Gottschling et al.83 The lampcontained 3 mg of sodium, 2 mg of mercury and 0.5 mg of cesium with 30 kPaof xenon fill gas and had a CRI of 70. The lamp, operated at 70 W, had 1000current pulses per second superimposed in-phase upon a supply voltage in theform of a 1 kHz square-wave current of 0.1 A. The CCT was 3600 K and theefficiency was B75 lm W–1.
7.7 Metal Halide Lamps
Metal atoms introduced into high-pressure mercury lamps give additionalspectral lines at visible wavelengths. Generally, metals are introduced as
Table 7.7 Effect of thallium on CCT.
Amalgam Composition (at.%) CCT (K)
Na–Hg – 2673Na–Tl–Hg 40:12:48 2523Na–Tl–Hg 50:25:25 3273
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iodides, bromides or even chlorides in some cases because of their much highervapor pressure. Many metal halide lamps contain rare earth metal halidesbecause of their rich spectral features in the visible range.84 Other metal halidelamps rely upon calcium iodide as an important part of the dose.85 Figure 7.9shows a spectrum of a metal halide lamp with a high CCT. It should benoted that mercury is present as a buffer gas. It also contributes several linesto the visible spectrum. Note the large continuum background in the400–650 nm range.
The spectrum from a metal halide lamp containing calcium iodide85 is shownin Figure 7.10; spectral features and efficiency of the 340 W lamp are as follows:luminous efficacy 105 lm W–1, CRI 90 and CCT 3860 K. The fill gas is aneon–argon Penning mixture with 98.0–99.5% neon.
Table 7.8 Light and electrical characteristics of lamps containing Na–Cs–Hgamalgam.
Alloy compositionVoltage(V)
Current(A)
Power(W)
Lightflux(lm)
Luminousefficacy(lm W–1)Hg Na Cs
0.3 0.60 0.10 104 4.5 404 29,570 730.3 0.55 0.15 122 4.5 405 29,420 720.3 0.50 0.20 117 4.2 413 26,710 640.3 0.40 0.30 44 5.7 250 13,600 540.3 0.30 0.40 150 3.2 378 14,300 370.2 0.65 0.15 109 4.6 425 20,300 450.2 0.50 0.30 143 3.5 376 24,230 650.2 0.40 0.40 87 4.9 380 12,240 320.2 0.725 0.075 71 5.1 333 32,890 980.1 0.825 0.075 123 4.0 422 27,470 65
nm
Figure 7.9 Spectrum of a 73W metal halide lamp containing TmI3 46.4 wt%,GdI3 23.2 wt%, NaI 19.6 wt%, TlI 5.8 wt%, InI 5.0 wt% and Hg1–10mg cm–3, with the following lamp characteristics after 100 h: CCT6000K, CRI 81 and efficacy 92 lm W–1.Reproduced from Ref. 84.
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V. Ruzicka and S. A. Rushworth, J. Chem. Eng. Data, 2010, 55, 4095.47. K. Ruzicka, M. Fulem and V. Ruzicka, J. Chem. Eng. Data, 2005, 50, 1956.48. J. D. Robinson, personal communication, 2005.49. K. Hilpert and I. Ali-Khan, J. Nucl. Mater., 1978, 78, 265.50. K. Hilpert, Ber. Bunsenges Phys. Chem., 1980, 84, 494.51. K. Hilpert, Ber. Bunsen. Phys. Chem., 1983, 87, 818.52. K. Hilpert, Ber. Bunsenges. Phys. Chem., 1984, 88, 37.53. K. Hilpert, Z. Metallkd., 1984, 75, 70.54. E. Fischer and H. Hoerster, US Pat., 5 109 181, 1992.55. L. F. Kozin, Physicochemical Properties of High-Purity Mercury and Its
Alloys, Naukova Dumka, Kiev, 1992.56. G. N. Rokhlin, Gas Discharge Sources of Light, Energia, Moscow, 1966,
p. 560.57. S. Anderson, US Pat., 4 216 178, 1980.58. S. Anderson, US Pat., 4 419 303, 1983.59. I. M. Veselnitsky and G. N. Rokhlin (eds), High–Pressure Mercury Lamps,
Energia, Moscow, 1971.60. E. V. Shpolsky, Atomic Physics, Nauka, Moscow, 1974, vol. 2, p. 240.61. K. Schmidt, in Proceedings of the 6th International Conference on Ionization
Phenomena in Gases, Paris, 1963, vol. 3, pp. 323.62. J. Maya, Appl. Phys. Lett., 1982, 40, 933.63. A. N. Zaidel, V. K. Prokofiev, S. M. Raisky and E. Ya. Shreider, Tables of
Spectral Lines, Nauka, Moscow, 1969.64. G. Hertzberg, Electronic spectra and electronic structure of polyatomic
molecules, Van Nostrand, Princeton, NJ, 1966.65. V. P. Glushko (ed.), Thermodynamic Constants of Substances, VINITI,
Moscow, 1972, Releases 5, 6, 10.66. V. S. Litvinov and A. N. Grigoryan, Trends in High-Pressure Sodium
Lamps with Improved Light Emission, Informelectro, Moscow, 1984, p. 31.67. M. B. Dergacheva, Yu. P. Petrenko, N. P. Petrenko and V. S. Litvinov, in
Physicochemical Grounds for Production of Metallic Alloys, ReportHighlights, Republican Conference, Almaty, 12–14 June 1990, Nauka,Almaty, 1990, p. 73.
68. L. F. Kozin, R. Sh. Nigmetova and M. B. Dergacheva, Thermodynamics ofBinary Amalgam Systems, Nauka, Almaty, 1977, p. 344.
69. M. B. Dergacheva, L. F. Kozin and O. Ya. Smirnova, in Thermodynamicsof Metallic Systems: Papers of the 4th National Meeting on
Lighting 161
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Thermodynamics of Metallic Alloys (Melts), Nauka, Almaty, 1979, Part 2,pp. 36–41.
70. M. B. Dergacheva, N. L. Panova, G. R. Hobdanergenova and L. F. Kozin,Zh. Fiz. Khim., 1984, 58, 305.
71. C. Hirayama, K. F. Andrew and R. J. Kleinowsky, Thermochim. Acta,1981, 45, 23.
72. R. Hultgren, P. D. Desai, D. T. Hawkins, M. Gleiser and K. K. Kelley,Selected Values of the Thermodynamic Properties of Binary Alloys,American Society for Metals, Metals Park, OH, 1973.
73. G. R. Hobdanergenova, Studies of Thermodynamic Properties of LiquidAlloys Based on Alkali Metals, Indium, Thallium and Mercury, Author’sSummary of a Dissertation for PhD in Chemistry, Almaty, IOCE,Academy of Sciences of the Republic of Kazakhstan, 1984, p. 29.
74. M. B. Dergacheva, Yu. P. Petrenko and G. R. Hobdanergenova, et al, Izv.Akad. Nauk Kazakh. SSR, Ser. Khim., 1976, 1, 54.
75. Y. Watarai, H. Yamazaki, N. Saito, M. Yamaguchi, T. Okamoto and H.Akutsu, US Pat., 4 109 175, 1978.
76. H. Mizuno, Jpn. Pat., 49-8548, 1974.77. L. F. Kozin, M. B. Dergacheva and G. R. Hobdanergenova, Electronic
Processes in Aqueous Solutions, Nauka, Almaty, 1981, pp. 36.78. L. F. Kozin, Yu. A. Meshcheryakov and R. Sh. Nigmetova, et al.,
Svetotekhnika, 1974, 8, 10.79. L. F. Kozin, Yu. A. Meshcheryakov and R. Sh. Nigmetova, et al.,
Svetotekhnika, 1977, 15, 8–9.80. G. R. Hobdanergenova, M. B. Dergacheva and L. F. Kozin, Izv. Akad.
Nauk Kazakh. SSR, Ser. Khim., 1983, 3, 8–12.81. G. R. Hobdanergenova, M. B. Dergacheva and L. F. Kozin, Zh. Fiz.
Khim., 1983, 57, 2059.82. A. J. Heethling, J. Chem. Thermodyn., 1975, 7, 73.83. W. Gottschling, K. Guenther, H.-G. Kloss, R. Radtke and F. Serick, US
Pat., 4 963 796, 1990.84. A. Genz, US Pat. Appl., 2011/0204776, 2011.85. R. Gibson, T. Steere and J. Tu, US Pat. Appl., 2011/0266955, 2011.
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CHAPTER 8
Synthesis of SemiconductingCompounds
8.1 Synthesis of Semiconducting Mercury Compounds
Chalcogenides, halides, chalcohalides and other compounds of mercury exhibitsemiconducting properties. The chalcogenides HgS, HgSe, HgTe are n-typesemiconductors. Figure 8.1 shows the phase diagrams for mercury chal-cogenides. For all three systems it is typical to generate only one equiatomiccompound. The melting point of the equiatomic compounds are as follows:
HgS 825� 2 1C1
820 1C2
HgSe 799 1C3
793 1C4 at a mercury vapor pressure of 9.12�106 Pa4HgTe 686 1C5
670 1C1
There are three modifications of mercury sulfide (HgS) in the Hg–S system.The red a-modification of cinnabar (cinnabarite) is stable from roomtemperature up to 315–345 1C. It forms a hexagonal lattice. At intermediatetemperatures, from 316–346 to 470–481 1C, the black b-modification (meta-cinnabarite) is stable. It forms a cubic lattice with a¼ 0.5852 nm. At hightemperatures, from 470–481 to 788–804 1C, the bright red g-modification(hypercinnabarite) is stable. It forms a prismatic lattice with a¼ 0.686 andc¼ 1.407 nm.1–3 The solubility range of solid mercury sulfide is narrow and itmelts congruently at 820 1C (1093K). It is also apparent, from Figure 8.1, thattwo monotectic reactions occur in the Hg–S system. These reactions:
L2 "L1 þ g�HgS
Mercury Handbook: Chemistry, Applications and Environmental Impact
By Leonid F Kozin and Steve Hansen
r L F Kozin and S C Hansen 2013
Published by the Royal Society of Chemistry, www.rsc.org
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and
L2 " g�HgSþ L3
occur at 800 and 790 1C, respectively. Mercury sulfide evaporates congruentlythrough a dissociation mechanism. When evaporating, HgS dissociates with adegree of dissociation close to 1 and decomposes into gaseous atoms ofmercury and S2 molecules.2,6 Novoselova and Pashinkin6 recommend thefollowing equations for the characterization of the total pressure of HgS:
log ðptot; PaÞ¼ � 6200=Tþ 12:3909 ð8:1Þ
log ðptot; PaÞ¼ � 5814=Tþ 11:7879 ð8:2Þ
(a)
(b)
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The heat of evaporation of HgS is 183.4 kJ mol–1 and its thermodynamicparameters are1,7 DG�298:15¼� 52.42 kJmol–1, DH�298:15¼� 58.99 kJmol–1 and
DS�298:15¼ 82.42 Jmol–1K–1.
Cinnabar is the main mineral in mercury deposits.8 Cinnabar (a-HgS)exhibits photoconductivity and is highly sensitive to electromagnetic andX-radiation.
In the Hg–Se system, mercury selenide (HgSe) forms a face-centered cubicsphalerite structure with a¼ 0.608 nm, which is stable from room temperatureup to 799 1C (872K).3 Sharma, Chang and Guminski9 reported pure HgSe isstable up to 799 1C (1072K). According to Brebrick,10 the vapor pressure aboveHgSe is equal to the sum of the pressures of mercury and selenium vapors. NoHgSe molecules were found in studies employing the method for themeasurement of the optical density of vapors above solid HgSe at 450–816 1C(723–1089K).10 The pressure of the saturated vapor of mercury selenides in thetemperature range 340–770 1C (613–1043K) is described by the equation
log ðp; PaÞ¼ � 6445=Tþ 11:7349 ð8:3Þ
Thermodynamic parameters of HgSe are7 DG�298:15¼ –53.748 kJmol–1,
DH�298:15¼ –59.413 kJmol–1 and DS�298:15¼ 99.035� 0.837 Jmol–1K–1.
Mercury selenide can be obtained with both n- and p-type conductivity; itfalls into the category of narrow bandgap semiconductors where the bandgap isDE¼ –0.07 eV.1
HgTe is also a narrow bandgap semiconductor (DE¼ –0.02 eV1). Understandard conditions, HgTe has a face-centered cubic lattice with a¼ 0.646 nm.3
At a pressure of B1.4�103 MPa, the cubic lattice changes into a hexagonal
(c)
Figure 8.1 Phase diagrams of the systems (top) Hg–S [9a], Hg–Se [9b] and Hg–Te [9c].a) R. C. Sharma, Y. A. Chang and C. Guminski, J. Phase Equilibria, 1993,14, 100. b) R. C. Sharma, Y. A. Chang and C. Guminski, J. Phase Equilibria,1992, 13, 663. c) R. C. Sharma, Y. A. Chang and C. Guminski, J. PhaseEquilibria, 1995, 16, 338.
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cinnabar structure.3 Solid HgTe provides for very limited solubility of Hg andTe. Mercury telluride evaporates incongruently through the following reaction:11
HgTesolid ! TesolidþHggas ð8:4Þ
The degree of dissociation is close to 1 while the mercury partial pressure isgreater than the tellurium partial pressure almost by two orders of magnitude.2,12
Partial pressures of mercury and tellurium in the Hg–Te system were foundthrough the determination of optical density.13 The relationship betweenmercury telluride vapor pressure and temperature in coordinates logp–1/T islinear and, according to various authors, is described by the equations
log ðp; kPaÞ¼ �5251:3T
þ 9:1549 at 486� 600 k1 ð8:5Þ
and
log ðp; kPaÞ¼ �5700� 200
Tþ ð8:30� 0:40Þ at 480�730 k:11 ð8:6Þ
Analysis of experimental data11 for the temperature range 435–950Kresulted in the following vapor pressure equation:
log ðp; kPaÞ¼ �5700Tþ 8:18 ð8:7Þ
The standard enthalpy change for HgTe upon evaporation isDH�298:15¼ 107� 4 kJmol–1, while the entropies of vaporization at 500, 550
and 600K are DS¼ 110.5, 110.2 and 109.9 Jmol–1K–1, respectively.11
Thermodynamic parameters of HgTe are7 DG�298:15¼� 28.033 kJmol–1,
DH�298:15¼ 32.175 kJmol–1 and DS�298:15¼ 111.50� 0.628 Jmol–1K–1.
Mercury sulfides, selenides and tellurides form solid solutions with sphaleritestructures14–16 between themselves and also with chalcogenides of subgroupsIIB–VIB of the periodic table. These solutions allow one to obtain materialsused in optoelectronics and microelectronics.1,4–6,8,12–20 For instance, singlecrystals of solid solutions of HgS–HgSe, HgSe–HgTe and others are used forthe manufacture of photoconductive infrared detectors in optoelectronics (lightsources and receivers, Raman lasers, light flux control devices), in ionizingradiation detectors, in generators and amplifiers of acoustic and microwave-band oscillations, etc. Materials based on solid solutions of CdxHg1–xS,CdxHg1–xSe, CdxHg1–xTe and HgxMn1–xTe have been extensively used inoptoelectronics, microelectronics and other fields of advanced technology.These n-type semiconductors are used for the manufacture of photoconductiveinfrared detectors with a pronounced maximum in the 0.3–12 mm band.Figure 8.2 shows quasi-binary phase diagrams of HgS–CdS, HgTe–CdTe andHgTe–MnTe based on data of Mizetskaya et al.15 It is apparent fromFigure 8.2 that the mutual solubility of the components in the solid statedepends on the temperature. In the HgTe–CdTe system (Figure 8.2b), a broadfield of solid solutions can be seen. The large temperature range between theliquidus and solidus curves in the middle part, greater than 100 1C, makes itdifficult to obtain homogeneous crystals.
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A number of studies have been aimed at crystallization patterns of solidsolutions of HgxCd1–xTe, owing to the great importance of tellurides ofmercury for advanced infrared technology and outer space optoelectronics.That is why there are stringent requirements on homogeneity, whichresearchers are trying to meet in both ground-based laboratories1,15–21 and inthe weightlessness conditions in space.22–25
Solid solutions of HgTe–CdTe and HgTe–MnTe systems (manganese–mercury–tellurium a-phase) have identical band structures and closeelectrophysical properties. The structure of the HgTe–MnTe equilibriumdiagram has not been fully established.21 From Ref. 21, it is clear that the a-fieldof solid solutions is stable up to 35 at.% MnTe. At higher concentrations, thea-solid solution breaks down into MnTe2 and a mercury-enriched a-phase.Manganese–mercury–tellurium a-phase crystals feature high homogeneity and n-type conductivity. At 77K, the average concentration and charge carrier mobilityin Mn–Hg–Te single crystals are 2.6�1015 cm–3 and 2.6�104 cm2V–1 s–1,respectively.20
Close parameters are demonstrated by crystals of Hg1–xMnxTe (x¼ 0.125),synthesized from high-purity Hg (7N), Mn (9N) and Te (6N) at around 800 1Cfor 24–48 h and subjected to solid-phase recrystallization in mercury vapor ataround 750 1C for 320 h. The grown crystals had n-type conductivity at roomtemperature (average concentration of charge carriers m¼ 2�1016 cm–3) andp-type conductivity at 77K (m¼ 1016 cm–3).19
Figure 8.2 Phase diagrams of the quasi-binary systems, HgTe–CdTe.Reproduced with kind permission from Springer ScienceþBusiness Media.Landolt-Bornstein – Group IV Physical Chemistry Selected SemiconductorSystems Volume 11C1 2006 Non-Ferrous Metal Systems Part 1, Ed.G. Effenberg, S. Ilyenko, Springer, 2006, 267. Ref. 80.
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Mercury and cadmium and mercury and zinc chalcogenides display highphotosensitivity, which depends on the structural and chemical (purity)homogeneity of the single crystals. The impurity content in the input materialsHg, Te, Cd, Mn and Zn used for the synthesis of chalcogenide-based semi-conductors should not exceed 3�10–9 mass%.26
Chalcogenides can be used as a base for the synthesis of both high- and low-resistance electrooptic crystals, which demonstrate photoconductivity incrystals with electrical resistivity ranging from 1 to 1018O cm, with the life offree carriers, which determines photosensitivity, ranging from tens of minutesto 10–12 min according to Petrovsky et al.25). Mercury chalcogenides Hg3X2Y2
(where X¼ S, Se, Te; Y¼Cl, Br, I), which demonstrate high optical activity,electrooptical effects and photoconductivity,27 are valuable for opto- andmicroelectronics.
Semiconducting mercury compounds decompose when heated.28 The vaporpressures of mercury chalcogenides and chalcohalogenides becomeconsiderable during melting and crystallization. The pressures of mercuryvapor at the melting points of HgS, HgSe and HgTe are as follows:
HgS 5.82�106 PaHgSe 5.28�105 PaHgTe B3�106 Pa
Very high vapor pressures of mercury sulfide, selenide and telluride often causeampoules to burst. Therefore, during the synthesis of mercury chalcogenides,protective counter-pressure containers are often used. These containers are alsoused for cadmium–mercury–tellurium recrystallization in zero gravity.22,23,25
Therefore, to avoid losing a component during the synthesis of semi-conducting mercury compounds, the operation should take place in an enclosedvolume with ampoules heated to temperatures that exceed the vapor conden-sation temperatures of the volatile components. To prevent ampoules frombreaking at high temperatures, the ampoule with the synthesis components isplaced inside a sealed container filled with an estimated amount of inputcomponents to ensure an equivalent counter-pressure.15,22,28 This is the so-called ampoule method. The method completely eliminates any loss of thecomponents (oxidation, carry-over). The ampoules are made of high-purityfused-silica glass, i.e. quartz tubes. Methods for the synthesis of mercurychalcogenides HgX (X¼ S, Se, Te) and solid solutions of the type HgxMe1–xX(Me¼Cd, Mn, Zn, etc.) have been described.1,4–6,8,14,15,20,22,23,29
Semiconducting mercury compounds are synthesized using direct orindirect methods. Direct methods include synthesis from pure components inelemental form, from the gas phase andmelt according to the following equations:
Hgþ Te! HgTe ð8:8ÞHgþ Se! HgSe ð8:9ÞHgþ S! HgS ð8:10Þ
xHgþ ð1� xÞCdþ Te! HgxCd1�xTe ð8:11Þ
xHgþ ð1� xÞMnþ Te! HgxMn1�xTe ð8:12Þ
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Chalcogenide synthesis is performed in high vacuum at backgroundpressures of 10–3–10–5 mmHg [(13.3–0.133)�10–2 Pa] or in an inert atmospherein a three-section oven, at temperatures T1, T2 and T3, ensuring vaporization ofmercury (section one) and tellurium (section three) and their interaction insidethe reaction chamber (section two), where the vapors of mercury andchalcogens mix, react and form homogeneous nuclei, which crystallize on asolid surface layer by layer, creating a densely packed surface.
Direct synthesis methods also include the method of cultivating chalcogenide(cadmium–mercury–tellurium, manganese–mercury–tellurium) crystals in theliquid phase with one of the components (tellurium, cadmium, mercury)present in excess. Guminski30 shows a plot of the solubility of CdTe in mercury,according to Guminski.30 It can be seen that the function logSCdTe versus 1/T islinear and, as shown by Guminski,30 is described by
logSCdTe¼�3070
Tþ 3:68 ð8:13Þ
in the temperature interval 500–1250K. At 298K, the solubility of CdTe in Hgis 2.4�10–7 at.%.
Special attention has been devoted to studies of the equilibrium between solidCdTe and its saturated amalgam, which is characterized by the solubility product:
Lp¼ ½Cd�½Te� ð8:14Þ
A reaction occurs between equimolar amounts of cadmium and tellurium inmercury according to the equation
CdðHgÞ þ TeðHgÞ"CdTe#þ1Hg ð8:15Þ
However, if tellurium is in excess with respect to cadmium in Cd–Te–Hgsolutions, some amount of mercury becomes engaged (jointly deposited) withthe residuum, according to the stoichiometry of the reaction
xCdðHgÞ þ TeðHgÞ"CdxHg1�xTe#þ1Hg ð8:16Þ
The affinity of cadmium and mercury that are part of Cd–Hg–Te system is veryhigh; therefore, if tellurium is in excess with respect to cadmium, CdxHg1–xTewill be in equilibrium with the liquid phase of the solution. According toVydyanath,31 the activity coefficients of mercury and cadmium in epitaxiallayers of Hg0.65Cd0.35Te, grown on CdTe substrates at 550 1C, are gHg¼ 0.143and gCdo6.8�10–5, respectively.
The activity coefficients of cadmium are close to gCd for the tellurium-enriched binary alloy CdTesolid. Therefore, in several papers,15,18 reaction (8.16)is used for the synthesis of solid solutions of cadmium–mercury tellurides. Thisreaction is used to perform recrystallization of CdxHg1–xTe and grow singlecrystals.15,18,20,22–26,29 For industrial-scale production, chalcogenide singlecrystals are grown in autoclaves32 with programmed temperature ramps.Cruceanu and Nistor33 grew Hg1–xZnxTe single crystals from a mercurysolution. They dissolved 5 at.% Hg1–xZnxTe in mercury and grew the crystals
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in vacuum-sealed quartz ampoules at o923K at a cooling rate of 6Kmin–1.However, because of the high cooling rate, the resulting crystals featured highdislocation densities.
8.1.1 Sublimation and Resublimation Methods
To crystallize solid CdxHg1–xTe solutions, resublimation of input binary chal-cogenides CdTe and HgTe in an inert atmosphere is used. The crystals are grownin two-section electric furnaces; one of the designs is shown in ref. 15. Section oneof the oven, used for trays with the input material, has the maximum temperature(T2), and the end product section the minimum temperature (T1). In section oneat T2 the original chalcogenide evaporates and, with the help of a carrier gas, iscarried over to section two with a low temperature T1 where conditions aresuitable for vapor condensation due to supersaturation (T1{T2) and crystalli-zation. The structure of the crystals depends on the degree of supersaturation,cooling rate, flow rate and other factors.
Therefore, to obtain complex semiconducting compounds and their singlecrystals, a two-phase process is used. Phase one consists in preparing binarycompounds of mercury telluride and cadmium telluride and melting thesetogether to obtain cadmium–mercury telluride (CdxHg1–xTe) of the requiredproportions. In phase two, the compounds obtained are used to grow singlecrystals of solid solutions of CdxHg1–xTe using sublimation,15 zone melting viasolution in tellurium melt20 and recrystallization from melt.15,22–23 Studies ofHg1–xCdxTe recrystallization in zero gravity conditions demonstrated thatthe quality of crystals depended, as in normal gravity conditions,20 on growthrate.22,23 At growth rates below 3mmh–1, the experiments produced a homo-geneous Hg1–xCdxTe specimen with usable output of 50% of input materialvolume.22 The resulting homogeneous specimen was different from thatobtained on Earth under the same thermal conditions22 and demonstratedp-type conductivity. At T¼ 50K, the concentration and charge carrier mobilitywere 1017 cm3 and 100 cm2 s–1. According to Galonzka et al.,22 low carriermobility was due to a high dispersion at defects.
The annealing of Hg1–xCdxTe specimens in mercury vapor at 265 1C for6 weeks produced n-type specimens with concentration and charge carriermobility of (2.5–4.0)�1016 cm3 and (6–9)�104 cm2 s–1, respectively (theoreticalmobility 1.9�105 cm2 s–1).22 Earth-grown Hg1–xCdxTe single crystals producedunder the same conditions had cellular substructures, consisted of grains of highdislocation density (around 106 cm–2), and contained second-phase impurities.
It should be mentioned that the crystallization conditions of solid solutionsof Hg1–xCdxTe, Hg1–xMnxTe and Hg1–xCdx–xMnyTe have been the subject ofmany studies, as these materials have physicochemical and electrical propertiesof great value for fiber-optic communications, infrared equipment andoptoelectronics.34–42
8.1.2 Methods Used to Grow Single Crystals
The Bridgman method and its modifications are commonly used to growsingle crystals of solid solutions of Hg1–xCdxTe. In order to obtain a planar
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crystallization front, Bagai and Borle43 placed the ampoule with itsflat bottom slanting along the horizontal axis in a position offset withrespect to the vertical axis of the oven, which created a specifictemperature gradient along the crystal bar. The input components – high-purity mercury, cadmium and tellurium – were loaded into theampoule, which was evacuated to a pressure of 10–5mmHg (1.33�10–3 Pa)and sealed. The synthesis of single crystals or polycrystals of HgCdTefollowed at a growth rate of 1.0–4.5mmh–1 and a vertical temperaturegradient of 450K cm–1. The described method helped to improve thehomogeneity of HgCdTe crystals. A modified Bridgman method was used togrow single crystals of more complex systems – quaternary solid solutions ofCdxZnyHg1–x–yTe.
44
The solid solutions of this system outperform the solid solutions ofthe quasi-binary system HgTe–CdTe in terms of their physicochemicaland electrical properties, because they have higher melting points, greatermechanical strength, better deformation resistance and better time-independent photosensitivity. In this case, the crystals were synthesizedin thick-walled quartz ampoules from the input components (in at.%) 50%Te, 36% Hg, 12.5% Cd and 1.4% Zn. These were held for 50 h at atemperature 30 1C above the liquidus temperature while being continuouslystirred. Single crystals of solid solutions of the Hg–Cd–Zn–Te system weregrown in an ampoule traveling at a rate of B1 mm h–1 inside the oven with atemperature gradient of B40 K cm–1. For homogenization, the crystal wasannealed at 550 1C for 250 h.44 Specimens cut out of the crystal demonstratedn-type conductivity with an electron concentration of 3�1015–1�1017 cm3 anda mobility of B106 cm2V–1 s–1. Property mapping of CdxZnyHg1–x–yTe andCdxZnyHg1–xTe crystals showed that zinc-containing crystals havegreater stability and strength. According to Virt et al.,45 the high plasticityof CdxHg1–xTe contributes to the formation of structural disturbances:spots of integrity failure surrounded by areas of increased dislocationdensity, and ultimately redistribution of components. It has been establishedthat mechanical disturbances in the CdxHg1–xTe crystal structureresult in local breakdown of the solid solution either at the time ofmechanical attack or during subsequent improper storage of the crystalsand crystal-based products under natural conditions.45 Interestingly,according to Vasiliev et al.,46 the stability of solid solutions(CdTe)x(HgTe)1–x in the pseudo-binary system CdTe–HgTe decreases withdecrease in temperature. Vasiliev et al.46 gave the integral Gibbs freeenergies of the formation of tellurium-saturated solid solutions of thissystem shown in Table 8.1.
8.2 Indirect Synthesis of Mercury Chalcogenides
Indirect synthesis methods for mercury chalcogenides also merit attention.These include methods in which at least one of the input components is usedin the form of a chemical compound. In this case, during synthesis, the
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components interact via exchange or oxidation–reduction reactions accordingto the following equations:
HgCl2 þNa2S! HgSþ 2NaCl ð8:17ÞHgBr2 þH2Te! HgTeþ 2HBr ð8:18ÞHgþNa2S6 ! HgSþNa2S4 ð8:19Þ
HgCl2 þH2Te! HgTeþ 2HCl ð8:20Þð1� xÞHgCl2þ xCdCl2þH2Te! Hg1�xCdxTeþ 2HCl ð8:21Þ
ð1� xÞHgBr2þ xCdBr2þH2Te! Hg1�xCdxTeþ 2HBr ð8:22Þ
These reactions also demonstrate the high affinity of chalcogens towardscadmium and mercury and also zinc, which permits the formation of binarychalcogenides of the type AIIBVI (A¼Zn, Cd, Hg; B¼ S, Se, Te) and pseudo-binary systems AIIBIV–AIIBVI.1,15
8.2.1 Transport Reactions Method
Semiconducting compounds of mercury and chalcogenides and solid solutionsbased on them are produced using transport reactions.16,17,47–58 Transportreactions are also used for fine purification and cultivation of single crystals,films and epitaxial layers. The chemical transport of Hg–Te and Hg–Cd–Tesystem components occurs via reversible heterogeneous solid–gas transportreactions at high temperature T2 and precipitation gas–solid reactions at alower temperature. Thus, the chemical transport of Hg–Cd–Te systemcomponents is accomplished with the help of NH4Cl,
47 NH4Br,59,60 NH4I,
60,61
HgI2,62 and I2,
63 while HgTe is produced using diethyltelluriumTe(C2H5)2–H2
64 and other organometallic compounds as carriers.16,17,38,47–58
For transport reactions, the transport and precipitation conditions in eachtemperature zone (Ti, Dpi, Ci, . . .) are adjusted so as to permit reactions inequilibrium conditions. The number of such chemical reactions even inrelatively simple systems, e.g. Hg1–xCdxTe–NH4Cl, Hg1–xCdxTe–NH4Br and
Table 8.1 Integral Gibbs free energy of formation of tellurium-saturated solidsolutions in pseudo-binary CdTe–HgTe.
xCdTe
–DGf (kJ mol–1)
600K 700K
0.01 0.42 0.500.2 1.04 1.181.3 1.50 1.660.4 1.80 1.970.5 1.92 2.100.6 1.94 2.150.7 1.89 2.140.8 1.69 1.961.0 0 0
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Hg1–xCdxTe–NH4I, may reach 21–25. Thus, the technology used to producehigh-purity Hg1–xCdxTe by precipitation via transport reactions in the systemHg1–xCdxTe–NH4X (X¼Cl, Br, I) produces the following gaseouscomponents:
1 Hg 6 CdX2 11 Te 16 H2Te 21 NH2
2 H2 7 HgX2 12 H 17 CdX 22 TeX2
3 HX 8 NH3 13 N 18 HgX 23 Cd4 N2 9 X2 14 CdH 19 N2H4 24 NH5 Te2 10 X 15 HgH 20 N3 25 N2H2
To analyze and select optimum conditions for an experiment to grow layersof solid solutions of Hg1–xCdxTe using the system Hg1–xCdxTe–NH4X(X¼Cl–, Br–, I–), Akhromenko and co-workers47,59–61 calculated the equi-librium composition of the gas phase and partial pressures of the componentsof the above systems. The total pressure in gas-phase composition calculationswas taken as the sum of the pressures of saturated vapors of mercury ortellurium (pTe2 ), plus the pressure generated by the products of reaction
between ammonium iodide and the solid matter. Temperature dependences ofthe partial pressures (in Pa) of mercury (pHg) and tellurium (pTe2 ) at the edge of
the homogeneity area in a system with NH4I on the side of Hg and Te forHg1–xCdxTe with x¼ 0.4 are determined according to the following equations:
log pHg¼ 0:193062� 10�4 þ 0:143345=T � 0:991008T � 10�7
� 8:951198� 105=T2 þ 0:34860485 logTð8:23Þ
log pTe2 ¼ � 4:00002þ 0:121644=T � 0:95965T � 10�7
� 2:214170=T2 þ 0:678135 logTð8:24Þ
whereas in iodide and bromide systems the transport of cadmium, mercury andtellurium is effected by dihalides of cadmium, mercury and ditellurium(Te2).
59–61 At high temperatures, T2, the partial pressures of these componentsare higher than at lower temperatures, which causes the mass transfer ofcadmium, mercury and tellurium into the zone with low temperature T1
producing the solid solution Hg1–xCdxTe.In chloride systems, metallic cadmium also takes part in mass transfer along
with CdCl2, Hg and Te2.47 At high temperatures in such systems, the partial
pressures of mercury-, cadmium- and tellurium-containing gaseous substancesare greater that at lower temperatures, which also determines mass transfertowards the low-temperature zone T1.
47 However, in ammonium halide systemscontaining solid solutions Hg1–xCdxTe, the partial pressure of Te2 increases byabout four orders of magnitude, the pressures of CdI2 and CdCl2 decrease byabout 1.4- and 7.2-fold, respectively, and the Hg pressure decreases 86-fold.47,61
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Transport reactions have also been used to obtain epitaxial layers of mercury-containing and other semiconducting compounds.16,17,42,48–58 Epitaxy iscontrolled deposition of single-crystal layers of semiconductors and theirsimultaneous alloying. Three methods are used to deposit epitaxial layers of solidsolutions over various substrates: (1) crystallization from solutions,42,65–67 (2)crystallization from the gas phase16,17,38,48–58 and (3) molecular beam epitaxy.68
8.2.2 Epitaxial Layer Growth
To grow epitaxial semiconducting layers of mercury-containing com-pounds AIIBIV and their solid solutions of AIIBIV–AiB
IV type A1–xAixB(e.g. Hg1–xCdxTe, Hg1–xZnxTe), the substrate (CdTe, CdZnTe, CdTeSe, GaAs,etc.) is introduced into a melt supersaturated relative to the epitaxial layercomponents at temperature T1.
42,65–67 Nevsky et al.67 described an experimentused to produce layers with x¼ 0.35 out of a solution of Hg0.203Cd0.022Te0.755 atT¼ 820–719K.
Interesting results were obtained via low-temperature liquid-phase epitaxy ofHg1–xCdxTe from tellurium-enriched melts of mercury.66 In this case, epitaxiallayers of solid solutions of Hg1–xCdxTe with xE0.2 were grown from solutionsof (Hg1–xCdz)1–xTey (where z¼ 0.056; y¼ 0.83–0.92 depending on temperature).The melt used to grow epitaxial layers was obtained by melting Te, HgTe andCdTe in a graphite tray immediately prior to the experiment. As substrates,12�12�1mm3 (111) CdTe crystals were used after chemical–mechanicalpolishing and etching. Epitaxial layers were grown from supercooled melts ofmercury. The temperatures of the growing zone and mercury vessel werecontrolled separately during the growth process. Epitaxial layers were grown attemperatures between 400 and 500 1C. For a growth temperature of 450 1C, thesaturation and homogenization of the solution were performed at 475 1C, i.e.,25 1C above the temperature of epitaxial layer growth. Layer growth begins witha 5 1C supercooling followed by cooling at a constant rate of 0.15 1C min–1. Theprocess produces epitaxial layers of solid solutions of Hg1–xCdxTe with lowdefect concentrations.42,66 Epitaxial layers of Hg1–xCdxTe can also be grownusing the thermal zinc ‘shift’ method of epitaxy.42
The process of growing epitaxial layers of mercury-containing semi-conductors suggested by Chiang and Wu 66 is very labor intensive and requireshigh-precision control. Therefore, the method of growth via the reaction ofthermal dissociation of compounds in the gas phase appears to be morepractical.16,17,38,48–58 Epitaxial layers of solid solutions of Hg1–xCdxTeare grown from the gas phase with the help of organometallic compoundsof tellurium (diethyl, dialkyl, dimethylallyl, diisopropyl telluride) andcadmium (dimethyl-, diethylcadmium) in a ratio of 1:1 and at a concentrationof 1�10–4 mol L–1 and metallic mercury.48–53,55–58 To grow epitaxial layers ofHgTe and CdTe, Brebrick13 used dimethylmercury, dimethylcadmium andmethylallyl telluride. The preferred use of high-purity metallic mercury ratherthan organomercuric compounds is dictated by its greater thermal stabilitycompared with other components at growing temperatures.48,69
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CdTe with (100) and (111)48,50–51,54–55 orientations, GaAs,38,51,58 InSb,54
HgCdTe,47 CdTeSe53 and Al2O3 (0001) – sapphire70 have been used assubstrates. Epitaxial layers were grown in horizontal and vertical reactorsat temperatures below 180 1C,49 225 1C,48 230–410 1C,55 250–350 1C,51,54
B370 1C,53 395 1C50 or 415 1C.38
Epitaxial films of Hg1–xCdxTe (at x¼ 0.3) with n-type conductivity have aHall conductivity of 2.3�104 cm2V–1 s–1 at 40 K and a carrier concentration3.5�1015 cm–3.58 Alloying with arsenic (AsH3) produced p-type conductivitywith a charge carrier concentration of 3.5�1015–1.1�1016 cm–3.58
Molecular beam epitaxy is not usually used for depositing epitaxial layers ofdecomposing semiconducting compounds. However, Faurie et al.68 used thismethod to obtain epitaxial layers of Hg1–xCdxTe with xE0.34 over a CdTesubstrate. Layers with a thickness of 12 mm were deposited at 195 1C. Theepitaxial layers demonstrated p-type conductivity, which was due to thepresence of mercury vacancies, as the layers were grown in excess tellurium.Charge carrier mobility and concentration in the epitaxial layer at 77K were8.0�102 cm2V–1 s–1 and 3.6�1015 cm–3, respectively, which were similar to thoseof the best specimens of solid solutions of Hg1–xCdxTe at x¼ 0.34.
Ion implantation of boron into the surface layers of p-type substratesHg1–xCdxTe (xE0.15) produced n-type semiconductors due to defects inducedby implanting. Bubulac71 used ion implantation (B or Be) to produce a series ofp–n junctions of different nature and electrical profiles that were used tomanufacture high-quality instruments based on Hg1–xCdxTe (xE0.2), with n-to p- or p- to n-type junctions with As implanted into the p-region and In asbackground into the n-region. Ion implantation (Hg, B, In) followed byannealing of epitaxial layers of Hg1–xCdxTe (x¼ 0.22–0.23) over CdTe andCdZnTe substrates in mercury vapor allowed Destefanis72 to achieve high-quality p–n junctions and produce diodes for matrix optical detectors.
Over the years, intensive research efforts have been dedicated to growingsemiconducting compounds, especially ternary compounds Hg1–xCdxTe,binary HgTe–HgI2 and ternary systems HgCdTe–HgI2, in microgravityconditions and in space.102–104 Special attention is being devoted to studies ofthe laws of mass transfer during seedless growth of bulk crystals, deposition ofepitaxial layers and the effects of microgravity on the homogeneity, structureand electrical properties of the above semiconducting compounds, comparedwith their Earth-made counterparts. It has been demonstrated that samples ofternary compounds Hg1–xCdxTe grown in microgravity have uniformcomposition and low segregation and are much more homogeneous. Theexperiments have demonstrated the advantages of microgravity processing ofHg1–xCdxTe crystals for various technologies, including annealing in mercuryvapor to produce crystals of uniform composition.75
In conclusion, it will be observed that the materials of type AIIBVI semi-conductors and derivative solid solutions are based on high-purity metallicmercury. The production of solid-state semiconductors and epitaxial filmsbased on solid solutions of Hg1–xCdxTe, Hg1–xMnxTe, etc., relies on theprocesses of alloying metallic mercury, cadmium and tellurium or mercury,
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manganese and tellurium, and in the case of films, on reactions of thermaldissociation of high-purity organic compounds of mercury, cadmium andtellurium or with a combination of thermal dissociation of dimethyl- ordiethylcadmium and the corresponding organic compounds of tellurium andthe interaction with high-purity metallic mercury vapor.
Among the important process operations is the annealing of Hg1–xCdxTe,Hg1–xZnxTe, Hg1–x–yCdxMnyTe in saturated vapors at 400–200 1C for24–170 h.58,73–77 Here the fundamental factor is the production culture, whichaffects not only the quality of technologically critical semiconducting materialswith tailored properties, but also the ecology of working areas and wholecommunities.78,79
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60. V. V. Ratnikov, V. N. Sorokin, V. I. Ivanov-Omskiy, K. E. Mironov,I. A. Gerko, V. K. Erganov and V. M. Merinov, Pisıma v JTF, 1988,14, 1410.
61. Yu. G. Akhromenko, G. A. Ilchuk, S. P. Pavlishin, S. I. Petrenko andO. I. Gorbova, Inorg. Materials, 1987, 23, 762.
62. H. Wiedemeier and D. Chandra, Z. Anorg Allg. Chem., 1987, 545, 109.63. D. Chandra and H. Wiedemeier, Z. Anorg Allg. Chem., 1987, 545, 98.64. L. I. Dyakonov, V. N. Ivlev and Y. I. Lipatova, Izv. Akad. Nauk SSSR,
Neorg. Mater., 1990, 26, 69.65. N. N. Berchenko, V. E. Krevs and V. G. Sredin, Semiconducting Solid
Solutions and Their Application, Voenizdat, Moscow, 1982, p. 208.66. C. D. Chiang and T. B. Wu, J. Cryst. Growth, 1989, 94, 499.67. O. B. Nevsky, Yu. I. Rastegin and V. A. Fedorov, Izv. Akad. Nauk SSSR,
Neorg. Mater., 1988, 24, 1963.68. J. P. Faurie, S. Sivananthan, M. Lange, R. E. Dewames,
A. M. B. Vandewyck, G. M. Williams, D. Yamini and E. Yao, Appl. Phys.Letters, 1988, 52, 2151.
69. J. M. Centeno, C. Gonzalez, J. Sanz-Maudes and T. Rodriguez, Mater.Lett., 1990, 9, 60.
70. E. R. Gertner, W. E. Tennant, J. D. Blackwell, J. P. Rode, J. Cryst.Growth, 1985, 72 , 462.
71. L. O. Bubulac, J. Cryst. Growth, 1990, 86, 723.72. G. L. Destefanis, J. Cryst. Growth, 1990, 86, 700.73. L. L. Regel, Sci. Technol. Rev. Space Explor. Ser., VINITI, Moscow, 1984,
21, 224.74. L. L. Regel, Sci. Technol. Rev. Space Explor. Ser., VINITI, Moscow, 1987,
29, 296.75. L. L. Regel, Sci. Technol. Rev. Space Explor. Ser., VINITI, Moscow, 1990,
34, 335.76. J. J. Kennedy, P. M. Amirtharaj, R. P. Boyd, S. B. Qadri, R. C. Dobbyn
and G. G. Long, J. Crystal Growth, 1990, 86, 93.77. T. Piotrowski, J. Cryst. Growth, 1985, 71, 453.78. F. C. Lu, P. E. Berteau and D. J. Clegg, Mercury Contamination in Man
and His Environment, Technical Reports Series No. 134, IAEA, Vienna,1972, pp. 67–85.
79. J. Vostal, Mercury in the Environment, CRC Press, Cleveland, OH, 1982,pp. 15–27.
80. Landolt-Bornstein – Group IV Physical Chemistry Selected SemiconductorSystems Volume 11C1 2006 Non-Ferrous Metal Systems Part 1, Ed.G. Effenberg, S. Ilyenko, Springer, 2006, 267.
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CHAPTER 9
Chlor-Alkali Process
9.1 Introduction
Early in the nineteenth century, Berzelius and Davy discovered that mercurycathode electrolysis of saline solutions of alkali metals, i.e. NaCl or KCl,produced liquid alkali metal amalgams. Upon contact with water, theamalgams decomposed and produced alkali metal hydroxides (MeiOH, whereMei is the one of the cations K1, Na1, Li1), hydrogen (H2) and the originalmercury (Hg). This experimental result was taken the basis for the industrialproduction of chlorine and alkalis, such as NaOH. The first patent for amercury cathode electrolyzer designed to produce chlorine and alkali wasgranted to Nolf in 1882 and the first Kastner bath-based industrial facility toproduce these chemicals was put into service in 1894 in Oldbury, UK.1–4
Industrial production of chlorine totaled 2.0 metric tons in 1950, 10 metrictons in 1975, 12 metric tons in 2000 and over 15 metric tons in 2010. Out ofthat quantity, over 7 metric tons of chlorine were produced via mercurycathode electrolysis of sodium chloride. The future of the chlorine and alkaliproduction method will depend on the future developments in the ‘chlor-alkali’process and in competitive methods, the so-called diaphragm and membraneprocesses.1,3 This chapter discusses electrochemical aspects of mercury cathodeelectrolysis, the metallurgy of the sodium–mercury system and the design ofelectrolysis units.
9.2 Electrochemistry of the Mercury Cathode Process
When dissolved in water, a salt, e.g. sodium chloride, dissociates into sodiumand chloride ions according to the equation
NaCl! Naþ þ Cl� ð9:1Þ
Mercury Handbook: Chemistry, Applications and Environmental Impact
By Leonid F Kozin and Steve Hansen
r L F Kozin and S C Hansen 2013
Published by the Royal Society of Chemistry, www.rsc.org
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In pure water, a much smaller number of molecules also dissociate into ions:
H2O! Hþ þOH� ð9:2Þ
and produce positively charged protons H1 and negatively charged hydroxylions OH–. The two ions carry the same charge but have different signs.Mercury(I) and -(II) reactions have the following standard electrodepotentials:5
Hg2þ2 þ 2e! 2Hg E� ¼ 0:788V ð9:3Þ
Hg2þ þ 2e! Hg E� ¼ 0:854V ð9:4Þ
In aqueous solutions, the zero charge potential of mercury is5
Ezero charge Hg¼ � 0:193V ð9:5Þ
versus the normal hydrogen electrode (NHE) and the standard electrodepotential of the sodium half-reaction:
Naþ þ e Ð Na ð9:6Þ
is E1¼ –2.728V.6 In 0.1 and 1.0M aqueous NaCl solutions, the zero chargepotential of mercury is Ezero charge Hg¼ –0.559V and –0.557V (versus NHE),respectively.5 Therefore, the surface of the mercury electrode in sodiumchloride solutions has a negative charge and, in concentrated solutionsdesigned for the cathode process, is described by the equation
Ei ¼E�Na þ2:303RT
zFlnCNaþ� fNaþ ¼E�Na þ
0:05912
zFlogCNaþ� fNaþ ð9:7Þ
where Ei¼ reversible electrode potential at ion concentration C, E�Na¼ normal
electrode potential of sodium, R¼ gas constant (J K–1mol–1), T¼ temperature(K), z¼ charge on the ion (for sodium z¼ 1), CNaþ¼ concentration of sodiumions (Na1) (mol L–1 solution), F¼Faraday constant (K mol–1) and fNaþ¼Na1
ionic activity coefficient.
9.3 Sodium–Mercury Phase Diagram
Sodium demonstrates a very strong affinity to mercury. The sodium–mercuryequilibrium phase diagram is given in Figure 9.1.7 The Na–Hg system ischaracterized by one congruently melting compound, NaHg2, melting atB340 1C,and five incongruently melting compounds which produce peritectic reactions.The incongruently melting compounds decompose via peritectic reactions:Na11Hg52 at B156 1C, NaHg at 215 1C, Na3Hg2 at 121 1C, Na8Hg3 at 66 1Cand Na3Hg at 60 1C.7 Na3Hg has a and b polymorphs and both NaHg andNa8Hg3 have a, b and g polymorphs. Appendix I considers these phases inmore detail.
Owing to the high affinity of sodium to mercury, the sodium amalgampotential becomes more positive compared with the sodium potential byaround 0.7V. The difference between the standard potentials of pure mercury
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and sodium [electromotive force (EMF)] is DE¼E�Hg � E�Na¼0.7973 –
(–2.728)¼ 3.5253V.5,6 As mercury interacts with sodium, the activity of sodiumis greatly reduced, its amalgam electrode potential shifts towards the electro-positive side and the real value of the EMF of the concentration cell is greatlyreduced. The potentials, in volts, of electrodes in actual sodium amalgamsystems may be calculated with the help of activity coefficients using thefollowing equations:
E¼ENaðHgÞ0 �
2:303RT
Fln
CNaþ fNaþ
CNa fNa
� �ð9:8Þ
E¼� 1:8490� 0:05915 logCNaþ fNaþ
CNa fNa
� �ð9:9Þ
The relationship of sodium and mercury activities in the Na–Hg system at375 1C, according to the literature,8–12 is given in Figure 9.2.
The activity curves of sodium and mercury demonstrate strong negativedeviations from ideal solution behavior. Formation of intermetallic compoundsoccurs even in liquid amalgams.11,12 In the dilute sodium region, activity is a linearfunction of concentration; at higher sodium concentrations, the sodium activity is
approximately proportional to the square of concentration, C2Na�Hg.
Studies of the physicochemical properties of amalgams prompted thedevelopment of the EMF analysis method, which consists in measuring theEMFs of amalgam concentration circuits of the type
Me Hgð ÞjMeþ;MeX;H2OjMe Hgð Þx ð9:10Þ
Figure 9.1 Structure of the Na–Hg equilibrium diagram.7 See Appendix I for moredetailed information about the Na–Hg phase diagram. HgNa has recentlybeen shown to be Na11Hg52.
7b
Reproduced with permission from Pergamon (Ref. 7b).
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In this case, the role of the reference electrode is played by diluted amalgam (onthe left-hand side) with a constant concentration of the studied metalthroughout the experiment. The potentials of each electrode of the cell withrespect to the NHE can be found from the following equations:
E1¼ constantþ 2:303RT
zFlogaMeiðHgÞ ð9:11Þ
E2¼ constantþ 2:303RT
zFlogaMeiðHgÞ ð9:12Þ
where constant¼E1þEs, and Es¼ � DGexc�
zF or Es¼ RT=zFð Þlng1, whereDG
excis the partial excess Gibbs free energy of Na in the amalgam, z¼ 1 and g1
is the activity coefficient of Me¼ sodium.11 Es values are a function of thechange in chemical potentials and EMFs of the concentration cells. Values ofEs are closely related to the structure of the Na–Hg equilibrium diagram. Thisproblem was addressed in detail by Kozin et al.11
Because the zero charge potential of mercury is –0.193V (versus NHE),i.e. more negative when compared with the equilibrium potential ofthe hydrogen electrode, mercury may dissolve slightly in an acidic solution, e.g.hydrochloric acid solution:11,12
2Hgþ 2HCl! Hg2Cl2 þH2 ð9:13Þ
NNa
0.0 0.2 0.4 0.6 0.8 1.00.0
0.2
0.4
0.6
0.8
1.0
123
Hg Na
Act
ivity
, a
Figure 9.2 Activities of the Na–Hg system components at 375 1C according todifferent authors: (1) Ref. 8; (2) Ref. 9; (3) Refs 10–12.
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Moreover, it has been established that in concentrated hydrochloric acid bothadsorbed and free molecular hydrogen are generated.11
The thermodynamic properties of the Na–Hg system at 375 1C, i.e. activities
of sodium and mercury, aNa and aHg, partial molar Gibbs free energies, DGNa
and DGHg, partial molar enthalpies, DHNa and DHHg, partial molar entropies,
DSNa and DSHg, and integral thermodynamic quantities DG, DH and DS, arepresented in Figure 9.3.11–14
Sodium–mercury amalgam forms extremely strong and weakly dissociatedintermetallic compounds. The structure of the Na–Hg equilibrium phasediagram and the activities of the components (sodium and mercury) areinterrelated. Formation of the intermetallic compounds in the Na–Hg systemleads to a negative departure of sodium and mercury activities from Raoult’slaw.11 Comparing the negative Gibbs partial and integral free energies with thestructure of Na–Hg equilibrium diagram also indicates that the system hasdeviated from the ideal solution law. Furthermore, the partial and integralenthalpies of mixing and partial and integral entropies of mixing also indicatethat Na–Hg system has deviated from the ideal solution law.11
Figure 9.3 The mercury cell process. In the mercury cell process, sodium forms anamalgam (a ‘mixture’ of two metals) with the mercury at the cathode. Theamalgam reacts with the water in a separate reactor called a decomposerwhere hydrogen gas and caustic soda solution at 50% are produced.Reproduced with permission from Ref. 3b.
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Bent and Forziati13 analyzed the EMF of dilute sodium amalgams and foundthat an amalgam containing NaHg4 (recently found7 to be Na11Hg52).Na11Hg52 has a free energy of formation DG¼ –20.2 kJ (mol atoms)–1.Deiseroth7 performed multiple studies on the intermetallic compounds presentin the Na–Hg system. His results and others are tabulated in Appendix I. Bentand Swift14 also calculated the free energies of formation of the intermetalliccompounds using the EMF method.
Recommended values for the excess Gibbs free energy and excess entropy of
mixing at infinite dilution are DGexc
Na ¼ –74.1 kJmol–1 and DSexc
Na ¼ –29.3 Jmol–1
K–1.11,12 The thermodynamic characteristics of sodium–mercury intermetalliccompounds at 18, 25 and 375 1Care given in Table 9.1. The highest negative partial
free energy values are for NaHg2 [DGNa¼ –23.3 kJ (mol atoms)–1] and Na11Hg52[DGNa¼ –20.2 kJ (mol atoms)–1]. Table 9.1 also shows that as the temperatureincreases from 18 to 375 1C, the integral enthalpy of formation of NaHg2 andNa11Hg52 decreases fromDH¼ –39.3 and –23.4 toDH¼ –17.0 and –12.7 kJmol–1,respectively.
9.4 Production of Chlorine
The production of chlorine, caustic soda (or potassium hydroxide) andhydrogen via mercury cathode electrolysis implies the use of graphite anodes.Anodes are normally treated with flax-seed oil in autoclaves at temperaturesr400 1C4 to reduce porosity. Over the past 25 years, a new anode technologyhas been introduced that uses sheets of titanium with oxidized surfaces coveredwith special microlayers of ruthenium, which after heat treatment turnthe surfaces into layers of ruthenium and titanium oxides, which constitutethe so-called oxides of ruthenium and titanium anodes (ORTA) that feature asmall chlorine overvoltage (ZCl2 ¼ 0.05V) and a higher oxygen overvoltage
(ZO2¼ 0.6V).3
The cathode, preferably composed of high-purity (99.9999%) metallicmercury, should be used during the electrolysis of chloride solutions. The
Table 9.1 Thermodynamic characteristics of intermetallic compounds ofsodium and mercury at 18, 25 and 375 1C.
Intermetalliccompound
VolumeratioNa, N1
DGNa14
[kJ (molatoms)–1]
DG14
[kJ (molatoms)–1]
DH(18 1C)15
[kJ (molatoms)–1]
DH(25 1C)16
[kJ (molatoms)–1]
DH(375 1C)8
[kJ (molatoms)–1]
DS(25 1C)14
(Jmol –1 K–1)
Na3Hg 0.750 –5.9 –11.5 –8.9 – –8.5 –92.0Na8Hg3
a 0.727Na3Hg2 0.600 –5.4 –17.2 –43.5 –19.2 –13.8 –87.0NaHg 0.500 –7.1 –20.7 –47.3 –21.3 –16.1 –90.0NaHg2 0.333 –23.3 –23.0 –39.3 –25.5 –17.0 –54.8Na11Hg52
b 0.175 –20.2 –15.1 –23.4 –16.7 –12.7 –27.2
a Stoichiometry was originally assigned as Na5Hg2.b Stoichiometry was originally assigned as NaHg4.
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technology used to obtain it is described in a Soviet Patent SU 401, 74717 andChapter 4. The patterns related to mercury cathode polarization duringelectrodeposition of sodium ions have been addressed.1–4 Several groups18–26
found that the sodium overvoltage is determined by the concentrationpolarization. De Nora,22 inventor of mercury electrode electrolyzers, foundthe sodium overvoltage to be 80mV on an amalgam containing 0.1 wt%Na at a temperature of 70 1C and a current density of 5250Am–2. Schmidtand Holzinger23 suggested an empirical equation for the relationshipbetween the cathode potential, E, of sodium amalgam and the currentdensity, i, in Am–2:
E¼ 1:81þ 0:000085i ð9:14Þ
However, from a theoretical point of view, E should have a logarithmicrelationship to i. Therefore, various workers18–26 undertook measurements ofthe amalgam cathode potentials of a horizontal electrolyzer with a mercurycathode. The electrolyzer had a bottom slope of 5 mm m–1 and was 30mm wideand 340mm long. The supply of brine of concentration 310 gL–1 NaCl andtemperature 75 1C was adjusted so that its concentration at the output of theelectrolyzer was 280–290 gL–1. A 1L bottle11 was provided in a mercuryrecirculation system upstream of the decomposer so that the amalgamconcentration did not fluctuate abruptly during the variable current densitytest. Amalgam was supplied at 300mLmin–1 or 100mLmin–1 cm–1 ofelectrolyzer width.
Polarized cathode potentials were measured by a salt bridge introduced viathe lid from the amalgam output side. The bent end of the salt bridge shouldtouch the amalgam surface. Potentials were measured with reference to asaturated calomel electrode. The results demonstrate the relationship betweenthe sodium overvoltage (Z) and the logarithm current density, i. The Tafelequation is then proposed:
Z¼ aþ blogi ð9:15Þ
with b close to RT/nF at n¼ 1. During the deposition of sodium, polarizationdecreases with growing amalgam concentration. The potential of the polarizedcathode, E, may be represented as the difference between the equilibriumpotential of the amalgam, Ep, and overvoltage, Z:
E¼Ep � Z ð9:16Þ
The relationship between polarization at a current density of 1A cm–2 andamalgam concentration is shown as a straight line 1 in Figure 9.6 and may beexpressed by the equation
Z ¼ 0:2� 0:33ffiffiffiffiffiffifficNa
pþ 0:068logi ð9:17Þ
where cNa is the sodium concentration (wt%) in the Na–Hg amalgam.
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There is also a relationship between the equilibrium potential of the amalgamand its concentration.18 In the amalgam concentration range 0.05–0.5 wt% Nathis relationship may be expressed as
Ep¼ � 1:68� 0:23ffiffiffiffiffiffifficNa
pð9:18Þ
By inserting values of Z and Ep from eqns (9.17) and (9.18) into eqn (9.2),we find
Ep¼ � 1:88� 0:068logi ð9:19Þ
Thus, according to Volkov and Klitsa,18 the polarized cathode potential doesnot depend on amalgam concentration. Table 9.2 illustrates the relationshipbetween cathode potential and amalgam concentration at a current density of10 000Am–2.
According to Volkov and Klitsa,18 the independence of the polarized cathodepotential and amalgam concentration means that the sodium activity at 75 1C isindependent of the composition. This is stipulated by the exchange equilibriumof the Hg–Na binary system and the invariability of the sodium activity,aNa¼ constant. Hence independence of the hydrogen discharge rate at theamalgam cathode from the sodium activity in the amalgam was proved on alaboratory electrolyzer model similar to that described by Bent and Forziati.13
The hydrogen discharge rate was measured via its chlorine content. The resultsof experiments performed by Bent and Forziati13 are in Table 9.3.
Table 9.2 Relationship between cathode potential and amalgam con-centration at current density 10 000Am–2 and 75 1C.
Amalgam concentration (wt%) Polarized cathode potential (V)
0.040 1.8980.070 1.9000.130 1.8980.180 1.8990.220 1.8990.300 1.9000.340 1.900
Table 9.3 Hydrogen content in chlorine at different amalgam concentrations.Current density, 0.5A cm–2; temperature, 60 1C; specific mercurysupply rate, 150mmmin–1 cm–1; bottom slope, 10mm.
Amalgamconcentration (%)
Hydrogen content inchlorine (%)
Amalgamconcentration (%)
Hydrogen content inchlorine (%)
0.02 0.29 0.34 0.580.03 0.29 0.45 0.490.05 0.38 0.50 0.330.10 0.50 0.60 0.400.18 0.56 0.65 0.500.20 0.46 0.70 0.34
Source: Ref. 13.
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The independence of cathode potential and its hydrogen discharge rate fromamalgam activity shows that the discharge rate of hydrogen ions is determinedonly by the cathode potential, i.e. only by the activity of sodium in the surfacelayer of the amalgam. According to Volkov and Klitsa,18 the sodium transferrate i (if we ignore the effect of the cathode layer thickness, since transfer occursfaster inside the layer than on the surface) can be described by
i¼ kv32cNa a ð9:20Þ
where v¼ average linear flow rate, cNa¼ sodium concentration in the surfacelayer of the amalgam and k¼ kinetic constant. Taking into account that theaverage linear flow rate v is related to specific inflow Q and layer thickness h by
v¼ Q
hð9:21Þ
and layer thickness h is related to specific supply Q and cathode inclination p by
h¼ k2Q12p�
13 ð9:22Þ
and by inserting eqns (9.21) and (9.22) into eqn (9.20), Volkov and Klitsa18
arrived at the equation
i¼ k3cNaQ34p
12 ð9:23Þ
where cNa is a function of cathode potential:
cNa¼ exp � nF E � E�ð ÞRT
� �ð9:24Þ
The hydrogen discharge current density is then another similar function ofcathode potential:
iH2¼ a Hþ½ �exp � nF E � E�ð Þ
2RT
� �ð9:25Þ
Therefore, eqn (9.23) may appear as follows:
i¼ k4 iH2
� 2Q
34p
12 ð9:26Þ
where, according to Volkov and Klitsa,18
iH2¼ k5i
12Qp�
14 ð9:27Þ
The current efficiency, C, is determined by the following relationship (if weignore current losses on reduction of active chlorine):
C¼� i � iH2
i¼ 1� k5
Q38p
14i
12
ð9:28Þ
Given Q and p as constants, eqn (9.28) becomes
C¼ 1� k6
i12
ð9:29Þ
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according to which the share of current spent for hydrogen discharge decreaseswith increase in current density, which is in agreement with experimental data.Equations (9.27) and (9.28) also agree with experience. For example, when thecurrent density in the baths was increased from 0.25 to 0.5 A cm–2, the specificmercury supply rate of 140mLmin–1 cm–1 was unchanged and the slope changedfrom 2 to 10 mm min–1. In accordance with eqn (9.28), the hydrogen content inchlorine decreased from 1.2 to 0.5%. The calculated value was 0.56%.
It should be remembered that it is difficult to perform an accurate verificationof eqns (9.27) and (9.28) owing to the high sensitivity of the hydrogen releaserate at the cathode and to impurities in the electrolyte and amalgam phase. Itshould also be mentioned that the derived relationships are only true whenthere is concentration polarization. The system will break down if the processtakes place at current densities that are lower than the exchange current densityfor the amalgam at a given concentration.
The process of mercury cathode electrolysis of sodium chloride has beenexamined in detail.1–4,17–23 During electrolysis, mercury was used in a closedcycle, which included cathode reduction of adsorbed sodium ions on thesurface of a negatively charged (Ezero charge Hg¼ –0.557 V versus NHE) mercurycathode, according to the reaction
Naþ þHg2� þ e! HgNaþads þ e! HgNa ð9:30Þ
at current densities of 5000–7500 A m–2. The concentration of sodium chloridein a carefully purified solution was 310� 5 gL–1.1 The cathode output ofsodium during the formation of sodium amalgam Na11Hg52 was 96%. ForORTA, the primary anodic output product (chlorine) reaches 99–99.9%(depending on the production ‘culture’). Therefore, the following processesoccur at the anode:
Primary process : 2Cl� � 2e! Cl2" E�Cl�=Cl2 ¼ 1:359V ð9:31Þ
Secondary process : 2H2O� 4e! O2" þ 4Hþ E�H2O =O2;Hþ ¼ 1:229V ð9:32Þ
The oxygen current efficiency is 0.1–1.0%. An electrolyzer made for anaqueous solution of sodium chloride with pump-driven circulation of themercury cathode within a closed cycle and with contact to the inserted graphiteelectrodes is illustrated in Figure 9.3. Upon contact of sodium amalgam withthe graphite electrode inserts, a galvanic element Cgraphite|NaHgn is formed, inwhich the functions of the anode are performed by the sodium amalgam andthose of the cathode by graphite.
Decomposition of sodium amalgam occurs as a result of operation of thegalvanic element, with release of hydrogen according to the reaction
1
11Na11Hg52 þH2O! NaOHþ 1
2H2 þ
52
11Hg ð9:33Þ
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The resulting sodium hydroxide solution with concentration 600–700 g dm–3
flows out from the decomposer into a collection tank. The decomposer alsooutputs the released hydrogen, which is then distributed to consumers or storedinto cylinders and gas tanks. The metallic mercury obtained according to eqn(9.33) is transferred into the electrolyzer for the next chlorine production cycleand to become sodium amalgam.
To date there are high-performance industrial mercury cathode elec-trolyzers.3,4 Key technical data on medium-capacity industrial electrolyzers areprovided in Table 9.4.
All mercury cathode electrolyzers consist of the following parts: electrolysisbath, sodium amalgam decomposer and mercury pump (mechanical orelectromagnetic). Industry uses monopolar horizontal electrolyzers. Allelectrolyzers are designed similarly and consist of the following three elements:one-piece flat steel bottom, rubber-coated steel frame and mercury electrolyzerlid.3,4
The P-101 mercury electrolyzer, shown in Figure 9.3, is a widely used model.The P-101 commonly uses a one-piece steel flat bottom that is 13.2 m long and1.2 m wide. The frame and lid consist of two parts connected via a flange. Thebottom supports a rubber-coated steel frame. The frame has two pockets –alkali and acid. All these elements together form an electrolyzer housing.
The alkali input chamber is located on the mercury pump side and the acidchamber is located on the opposite side. The pockets are equipped withmercury and liquid valves which seal the electrolyzer from gaseous hydrogen,chlorine and liquid. The electrolyzer is topped with a rubber-coated lid, whichaccommodates 284 sealed graphite anodes or ORTA. The anodes have gland
Table 9.4 Technical specifications of industrial mercury cathodeelectrolyzers1–4,18
Parameter
Ukrainian Others
P-101 P-20M P-300 De Nora KrebsHoechst–Uhde
Load (kA) 100 150 300 400 300 300Anode material Graphite Graphite ORTA ORTA ORTA ORTACurrent density(kA m–2)
5.3 7.85 10.4 12.5 12.0 12.5
Voltage (V) 4.4 4.6 4.3 4.0 4.25 4.25Currentefficiency (%)
95 96 96.5 96–97 96 95
Cathodedimensions (m)
14.5�2.4 19.4�1.95 19.7�2.3 14.8�2.3 14.4�1.61 12.5�2.4
Chlorine output(t day–1)
3.0 4.5 9.0 12.0 9.0 9.0
Mass of mercury incathode (t)
2.2 3.1 3.9 4.8 3.75 3.5
Power consumption(kWh t–1 ofchlorine)
3660 3780 3530 3020 3350 3300
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seals. The electrolyzer lid connects to the positive bus and its bottom connectsto the negative bus. Therefore, the lid and the bottom must be electricallyisolated.
The electrolyzer housing is insulated and mounted at a slope of 10 mm permeter of length. Mercury and electrolyte are supplied into the input pocket witha mercury pump. The anode reaction releases chlorine, while the cathodereaction forms dilute sodium amalgam, which flows into the amalgamdecomposer. The horizontal-type decomposer is located parallel to the mainhousing. The decomposer is a welded 13m long� 0.5m wide box sloping18 mm per meter of length (Figure 9.8) towards the side opposite that of theelectrolyzer.
The sodium amalgam decomposer outputs the resulting alkali, whichcontains NaOH 42–50 wt%, NaCl 0.01–0.05 wt%, Na2CO3 0.2 wt% and Hgup to 3 gm3.
A fairly high content of mercury in the alkali is due to the specifics of thebehavior of mercury during the mercury cathode electrolysis process. Differentmethods are used to reduce the mercury content in the end products. Thebehavior of mercury during amalgam electrolysis has been analyzed indetail.23–26 The cited studies offer different methods of reducing the mercurycontent in the end products.
Uhde (Germany) produces electrolyzers of various capacities, which dependon the cathode area.4 Available areas are 4, 15 and 35 m2. The design uses batchsuspension of anodes, which are either graphitized or metal oxide coated(ORTA). ORTA deliver chlorine gas, which contains Cl2 99.5 vol.%, CO2 0.2vol.%, H2 0.1 vol.% and air 0.2 vol.%. For graphitized anodes the figures areCl2 99.0 vol.%, CO2 0.6 vol.%, H2 0.2 vol.% and air 0.2 vol.%. The resultingcaustic soda (NaOH) solution has a concentration of 50% and contains 0.03%NaCl, 0.2% Na2CO3, 0.002% Fe and 0.05–3 mg L–1 of Hg.4
References
1. L. N. Sheludyakov, L. A. Saltovskaya and V. V. Stender, Appl. Chem.Mag., 1953, 26, 160.
2. J. Billiter, Die Technische Elektrolyse der Nichtmetalle, Springer, Vienna,1954.
3. (a) A. K. Gorbachov, Technical Electrochemistry, Prapor, Kharkov, 2002,p. 254; (b) Euro Chlor Institute, The mercury cell process. Available onlineat http://www.eurochlor.org/the-chlorine-universe/how-is-chlorine-produced/the-mercury-cell-process.aspx, Last accessed 21 June 2013.
4. G. I. Volkov, Production of Chlorine and Caustic Soda viaMercury–Cathode Electrolysis, Khimiya, Moscow 1968.
5. A. M. Sukhotin (ed.), Electrochemistry Handbook, Khimiya, Leningrad,1981.
6. G. Milaazzo and S. Caroli, Tables of Standard Electrode Potentials, Wiley,Chichester, 1978.
Chlor-Alkali Process 191
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7. (a) C. Hoch and A. Simon, Angew. Chem. Int. Ed., 2012, 51, 3029;(b) H. J. Deiseroth, Prog. Solid State Chem., 1997, 25, 73.
8. M. A. Bykova and A. G. Morachevsky, Appl. Chem. Mag., 1973, 46, 312.9. K. Hauffe, Z. Elektrochem., 1940, 46, 348.
10. M. L. Iverson and H. L. Recht, J. Chem. Eng. Data, 1967, 12, 262.11. L. F. Kozin, R. Sh. Nigmetova and M. B. Dergacheva, Thermodynamics of
Binary Amalgam Systems, Nauka, Alma-Ata, 1977, p. 343.12. R. Hultgren, P. Desai, D. Hawkins, M. Gleiser and K. Kelley, Selected
Values of Thermodynamic Properties of Binary Alloys, ASM, New York,1973.
13. H. E. Bent and A. F. Forziati, J. Am. Chem. Soc., 1936, 58, 2216.14. H. E. Bent and E. Swift, J. Am. Chem. Soc., 1936, 58, 2220.15. W. Biltz and F. Meyer, Z. Anorg. Chem., 1928, 176, 23.16. O. Kubaschewski, E. L. Evans and C. B. Alcock, Metallurgical Thermo-
chemistry, Pergamon Press, Oxford, 1967.17. L. F. Kozin, G. M. Cherniy and A. A. Nikotin, Method of Amalgam
refining of mercury in a four-section electrolyzer, USSR Pat., 401 747,Bulletin, 1973, (41), 109.
18. G. I. Volkov and Z. L. Klitsa, Elektrokhimiya, 1968, 4, 1347.19. L. S. Genin, Electrolysis of Sodium Chloride Solutions, Gostekhizdat,
Moscow, 1960, p. 208.20. Tekhnika, Development of a Chlorine Electrochemical Process,
http:www.industring.ru/chemical/chemical12.html, 2009 (in Russian) (lastaccessed 9 March 2013).
21. H. S. Schmidt and F. Holzinger, Chem.-Ing.-Tech., 1963, 35, 37–44.22. V. De Nora, J. Electrochem. Soc., 1950, 97, 346–351.23. L. F. Kozin and S. V. Volkov, Chemistry and Technology of High-Purity
Metals and Metalloids, Naukova Dumka, Kiev, 2002, vol. 1, p. 540 and2003, vol. 2, p. 351.
24. L. F. Kozin and Y. P. Sushkov, Ukr. Chem. Mag., 1991, 57, 611.25. L. F. Kozin, Ukr. Chem. Mag., 1991, 57, 733.26. V. De Nora, presented at the XXII Congres de Chimique Industrielle,
Barcelona, October 1949.
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CHAPTER 10
Use of Mercury in Small-scaleGold Mining
CEZARY GUMINSKI
Department of Chemistry, University of Warsaw, Warsaw, Poland
10.1 Introduction
Gold and mercury are metals that have been known since ancient times. Goldhas been known since antiquity and mercury was used as early as the fifthcentury BC. The two metals mix fairly easily and the first civilizations probablyused their ability to alloy with each other as both a gilding process and aprocess for extraction of gold from ore. Gilding was abandoned after the veryunfortunate incident that occurred in 1858 during the amalgamation gilding ofthe cathedral cupola in St Petersburg, when about 60 workers died frommercury vapor inhalation.1
Gold mining via mercury amalgamation was probably one of the firstmetallurgical extraction processes developed by humankind. Unfortunately,this dangerous practice persists to this day, largely unchanged since ancienttimes. Small-scale and artisanal gold mining continues in many sites around theworld and nothing suggests that this method, hazardous to people and theenvironment, will be abandoned soon. Although the use of mercury to extractgold is illegal in several countries, it still continues.
When mercury processing (distillation, reclamation, synthesis) is performedin industrialized countries, there are generally stringent restrictions concerningmercury release to the atmosphere. However, in regions where primitive, small-scale methods are performed in the open air, there is the potential to doconsiderable harm to the miners and the surroundings.
Mercury Handbook: Chemistry, Applications and Environmental Impact
By Leonid F Kozin and Steve Hansen
r L F Kozin and S C Hansen 2013
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10.1.1 Reasons for Artisanal Gold Mining
Mercury is a poisonous element without color or odor. Its toxic features are notimmediately manifested in the human body until some months or years afterexposure to mercury vapor. It is probable that the main reason why people indeveloping countries continually apply such ‘technology’ is because the effectsof poisoning with mercury are not obvious until some time after the exposure.Chapter 14 discusses the medical effects of metallic mercury poisoning.
The second reason is that performing this risky method is relatively cheapand the product (by contrast) is very expensive. Therefore, it is difficult toimagine that the procedure will soon be given up by artisanal gold miners, evenif they were properly informed about the irreversible damage that mercury andits compounds do to humans, animals and ecosystems.
10.1.2 Mercury Pollution
Small-scale gold mining is one of the largest sources of anthropogenic(human-made) mercury entering the atmosphere every year.2 The largestcontribution to elemental mercury is from burning of coal in power plants.Detailed studies of air, water and ground contamination in recent decadesestablished that about one-third of the world pollution with Hg in variousforms comes from small-scale gold mining. Owing to the strict regulationsapplied to industry in developed countries, one may predict that the amount ofHg emitted by official sources will decrease every year.
Mercury pollution from artisanal gold mining is likely to increase owing tothe high price of gold. On the other hand, secondary mercury emissions fromother sources, such as fossil fuels, dental amalgams, fluorescent lighting andincineration of medical and municipal waste, have been decreasing owing toelimination of mercury and environmental regulations.
10.2 Method of Artisanal Gold Mining
The extraction of gold particles by liquid mercury is relatively simple.Generally, the procedure is characterized by the following sequential stages:3
1. powdering of the ore containing gold2. enrichment of the crumbled ore for gold content3. mixing of the ore with mercury for gold extraction4. separation of excess mercury from the Au amalgam5. distillation of mercury from the concentrated Au–Hg amalgam6. purification of the gold alloy by remelting7. purification of mercury for its reuse.
The method may be applied not only to Au but also, with some modifications(with the use of Zn amalgam), to the extraction of Pt, Pd, Rh and Ir from ores.4
Gold is especially tractable for the amalgamation because it is easily wetted by
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mercury.5,6 If a drop of Hg is in contact with an Au surface, the Hg loses itshigh surface tension and is almost immediately (within seconds) propagatedover all Au surfaces. The process seems to be controlled by surface diffusionand at this stage it does not reflect a tendency of Au to form Au–Hg inter-metallics or a tendency towards dissolution and saturation of liquid Hg withAu (which is only 0.14 at.% Au at 298K) or solubility of Hg in solid Au (whichmay be estimated at about 13 at.% Hg at room temperature).7 Figure 10.1shows the binary Au–Hg phase diagram. The structures present in the diagramare discussed in Appendix I.
In practice, when drops of Hg contact small grains of Au, the Au particlesare very quickly soaked up inside the Hg drops. However, the real dissolutionprocess of Au and the formation of Au–Hg intermetallic compounds iscomparatively slow. If Au forms relatively large lumps in an ore, a miner is veryfortunate, since no further treatment, except Au remelting or refining, is notneeded. Unfortunately, such situations seldom arise.
The very traditional method of gold extraction from river sands starts withpanning, which is based on the significant density difference of Au (d¼ 19.3 g cm–3)and sand (dE2–3 g cm–3). This step concentrates Au particles. The next step isthe amalgamation of the particles with Hg. Gold ore in Au-containing rocksmust start as a fine powdery consistency. The particles of Au must be liberatedfrom the rock sheath to allow efficient contact with Hg, otherwise Hg would
Figure 10.1 The Au–Hg binary phase diagram.Reproduced with kind permission from ASM International.7
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not be able to wash out the gold grains. Miners who are able to automate thegrinding process use grinding mills, whereas those who are unable to do so usehand-operated mortars and pestles to crush the gangue into powder.
The next step is effective mixing of the river sands or the crushed Au ore withHg for about 1 h to form the Au amalgam. A discontinuous process is moreeffective than a continuous process. It may be performed in grinding mills, oncopper plates covered with the Hg or simply in pots. The amalgamation processis not effective when the Hg is contaminated with other metals or mineralsbecause small drops of Hg are covered with impurity particles on its surface andthe dirt may hamper its proper contact with Au grains. This situationfrequently occurs after reusing Hg. The wetting properties of Hg may beimproved by addition of an active metal (such as Zn) or by polarization of theHg in water with a battery to restore its bright surface. The wetting propertiesof Hg can also be significantly improved by a single distillation, although anadditional apparatus is needed.
The concentrate of Au amalgam thus formed may be further separated fromore by manual or mechanical panning or elutriation, since the sand and theamalgam have very different densities (2–3 and 413.5 g cm–3, respectively).Excess Hg is then removed from the Au amalgam by squeezing it throughleather, chamois or a fabric, and by centrifuging. The resulting Hg is, or shouldbe, reused and eventually purged of the impurities.
The concentrated Au amalgam obtained in this way is further heated and Hgis distilled off; this step should be performed at 700–800K (423–523 1C). Whenthe distillation is not complete, the remaining Hg is alloyed with Au. If thecontainer used for the distillation was made from a metal which readilycombines with Au (e.g. Zn, Fe, Sn), then the solid Au left after the distillationmay be contaminated by these metals and thus be less valuable. The distilled Hgis, or should be, carefully collected and reused.
In the last stage, the solid Au-rich alloy is remelted at about 1400K(1123 1C). Mercury and other volatile metals are released during this finaldistillation. This step is frequently carried out in a middleman’s shop in townsor villages. The last two steps (steps 5 and 6) should be performed in closedapparatus with coolers dipped in water to condense Hg. With proper distil-lation equipment, it is possible to reclaim and recycle 50–90% of the Hg in theamalgam.8
10.3 Environmental Degradation Caused by Small-scale
Gold Mining
Inexperienced miners typically introduce three types of environmental degra-dation while mining:
1. They discard tailings of the ore after the amalgamation step. Tailingscontain highly disintegrated Hg that is later washed into the ecosystemand can be converted into methylmercury.
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2. They distill Hg from the Au amalgam in the open air on a bonfire.Mercury is released directly to the atmosphere and travels long distances.
3. They remelt solid Au containing Hg in the open air.
Sometimes miners use nitric acid to dissolve Hg when Au is not dissolved.However, if the Hg is not subsequently reduced to its metallic state with the useof metallic Al, Zn or Fe, then this very toxic and corrosive solution producesmercury nitrate and creates very serious degradation of the surroundingecosystem.
Elemental Hg left on the Earth’s surface continuously evaporates. However,more harmful is the runoff into inland waters from the ore after the amalga-mation step. Metallic Hg is a noble metal with a low solubility in water(5.2�10–7 mol% at 298K). Its solubility is about 10% lower in sea water andgenerally decreases with increasing inorganic salt concentration.9 The majorityof Hg salts are also sparingly soluble in water. Surprisingly, Hg in both themetallic combined forms is readily absorbed by some bacteria living in watersand the most toxic organometallic compounds of Hg (methyl-, ethyl-,phenylmercury) are produced. These compounds further accumulate in fish andfinally enter the ecosystem.10,11 Therefore, every portion of the tailings, witheven small amounts of Hg discarded into waters, adds more Hg to theenvironment. Residues of Hg in the tailings left in the open air evaporatecontinuously and likewise contribute to pollution of the environment; however,such processes occur slowly.
Perhaps the worst procedure in the gold extraction process, unfortunatelysometimes applied by miners, is the use of cyanides for the extraction of tracesof Au left in ore that also contains Hg. The cyanide reacts not only with Au butalso with Hg, forming mercury cyanide compounds that are extremely toxic,especially when they run off into inland waters or are involuntarily acidified.
10.4 Remedies or Improvements to Small-scale
Gold Mining
Appealing to miners to keep Hg-containing ores in closed containers orcarefully to collect Hg and reuse it seems to be the only practical method ofprotecting wastes containing Hg from evaporation or from being discarded intowaters. The remainder of the Hg may also be trapped by contact of the ore withAg or amalgamated Cu plates, but such effective procedures are expensive.
It is much easier to convince miners to improve the Hg distillation processfrom the liquid and the solid Au amalgam (which the present authorexperienced during educational lectures in Peru). If the distillation is performedin a closed system (a retort made of steel, cast iron or enameled material) withan effectively cooled condenser made of metal that does not amalgamate withHg, then the Hg obtained in this way is fairly pure and can be reused manytimes for Au extraction.
A very detailed report on many aspects of small-scale of Au mining with theuse of amalgam techniques is available12 and also in a more condensed form.8
Use of Mercury in Small-scale Gold Mining 197
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References
1. S. I. Venetskii, Mercury, in Tales about Metals, Mir, Moscow, 1981, p. 186.2. L. D de Lacerda, Environ. Geol., 2003, 43, 308.3. M. M. Veiga, S. M. Metcalf, R. F. Baker, B. Klein, G. Davis, A. Bamber,
S. Siegel and P. Singo, Global Mercury Project Manual for TrainingArtisanal and Small-Scale Gold Miners, UNIDO, Vienna, 2006.
4. V. S. Shemyakin, K. A. Brik, S. P. Bukhman and K. A. Karasev, Izv. Akad.Nauk Kaz. SSR, Ser. Khim., 1979, 3, 73.
5. M. N. Gavze, Korroziya i Smachivaemost Metallov Rtutyu, Nauka,Moscow, 1969, p. 170.
6. H. Winterhager and W. Schlosser, Metall, 1960, 14, 1.7. H. Okamoto and T. B. Massalski, Phase Diagrams of Binary Gold Alloys,
ASM International, Materials Park, OH, 1987, 132.8. K. H. Telmer and M. M. Veiga, in Mercury Fate and Transport in the
Global Atmosphere: Missions, Measurements and Models, ed. N. Pirroneand R. Mason, Springer, Dordrecht, 2009, p. 131.
9. L. Clever, Mercury in Liquids, Compressed Gases, Molten Salts and OtherElements, IUPAC Solubility Data Series, vol. 29, Pergamon Press, Oxford,1987, p. 7.
10. R. Von Burg and M. R. Greenwood, Mercury, in Metals and TheirCompounds in the Environment, ed. E. Merian, VCH, Weinheim, 1991, p.1052.
11. I. Drabaek and A. Iverfeldt, Mercury, in Hazardous Metals in theEnvironment, ed. M. Stoeppler, Elsevier, Amsterdam, 1992, p. 257.
12. M. M. Veiga, P. A. Maxson and L. Hylander, J. Cleaner Prod., 2006,14, 436.
General References
P. A. Maxson, in Dynamics of Mercury Pollution on Regional and Global Scales,ed. N. Pirrone and K. R. Mahaffey, Springer, New York, 2005, p. 25.
J. O. Nriagu and J. M. Pacyna, Nature, 1988, 333, 134.E. G. Pacyna and J. M. Pacyna, Water Air Soil Pollut., 2002, 137, 149.J. M. Pacyna, J. Munthe, K. Larjava and E. G. Pacyna, in Dynamics ofMercury Pollution on Regional and Global Scales, ed. N. Pirrone andK. R. Mahaffey, Springer, New York, 2005, p. 51.
R. P. Mason, W. F. Fitzgerald and F. M. M. Morel, Geochim. Cosmochim.Acta., 1994, 58, 3191.
S. J. Spiegel and M. M. Veiga, J. Cleaner Prod., 2010, 18, 375.
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CHAPTER 11
Mercury Legislationin the United States
11.1 Introduction
The use of mercury is heavily regulated owing to its toxicity. Activities thatrelease mercury to the environment include chlor-alkali plants, steel and metalrefiners, coal-based power plants, artisanal and small-scale gold mining, cementproducers, municipal waste incinerators, dental amalgam, fluorescent andmetal halide lamps and disposal of mercury switches, barometers, ther-mometers, etc. Legislation on mercury occurs to some extent in most countries.A detailed look at all of the major directives regarding mercury from industrialcountries is beyond the scope of this book. European directives concerningmercury have been reviewed elsewhere.1 This chapter summarizes the regu-lation of mercury in the United States.
11.2 Mercury Legislation2
The following Acts of Congress have been promulgated for the control andreduction of mercury pollution in the United States. Specific to mercury are theActs:
� Mercury Export Ban Act (2008)� Mercury-containing and Rechargeable Battery Management Act (1996).
Other broader legislation controlling mercury release includes:
� Federal Food, Drug and Cosmetic Act (1938)� Federal Insecticide, Fungicide and Rodenticide Act (1947)� Clean Air Act (1970) and Amendments
Mercury Handbook: Chemistry, Applications and Environmental Impact
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r L F Kozin and S C Hansen 2013
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� Safe Drinking Water Act (1974)� Toxic Substances Control Act (1976)� Clean Water Act (1977)� Comprehensive Environmental Response, Compensation and Liability
Act (1980)� Superfund Amendments and Reauthorization Act (1986)� Emergency Planning and Community Right-to-Know Act (1986)� Resource Conservation and Recovery Act (1984)� Food and Drug Administration Modernization Act (1997).
11.2.1 Mercury Export Ban Act
The goal of the US Mercury Export Ban Act is to remove mercury from theworld market. In October 2009, the US Environmental Protection Agency(EPA) released its Report to Congress on Mercury Compounds.3 The report,required by Congress under Section 4 of the Mercury Export Ban Act of 2008(MEBA), identifies sources of mercury compounds in the USA and reportsquantities in imports, exports and uses of these compounds in products andprocesses. The report also assesses the potential for key mercury compounds tobe exported for reduction into elemental mercury. Table 11.1 gives the mercurycompounds included in the Report.
1. Specifically required for this report by MEBA.2. More than 25 000 pounds (11 340 kilograms) were produced at single site
in any single reporting year since 1986.3. Manufactured or imported as a specialty chemical.4. Technologically feasible to export and convert to elemental mercury
abroad.5. Produced in potentially significant quantities, including as a waste or
byproduct.
Table 11.1 Mercury compounds by criteria for inclusion in the Report toCongress on Mercury Compounds.3
Compound CAS No. Criteria for inclusiona
Mercury(I) chloride 10112-91-1 1, 2, 3, 4, 5Mercury(II) acetate 600-27-7 2, 3Mercury(II) chloride 7487-94-7 1, 2, 3Mercury(II) iodide 7774-29-0 3Mercury(II) nitrate 10045-94-0 3, 4Mercury(II) oxide 21908-53-2 1, 3, 4Mercury(II) selenide 20601-83-6 5Mercury(II) sulfate 7783-35-9 3, 4, 5Mercury(II) sulfide 1344-48-5 3, 5Mercury(II) thiocyanate 592-85-8 3Phenylmercury(II) acetate 62-38-4 2Thimerosal 54-64-8 3
aCriteria for inclusion:
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The Act’s three main provisions are as follows:
1. Federal agencies are prohibited from conveying, selling or distributingelemental mercury that is under their control or jurisdiction. This includesstockpiles held by the Departments of Energy and Defense.
2. Export of elemental mercury from the USA is prohibited beginning1 January 2013.
3. The Department of Energy (DOE) shall designate one or more DOEfacilities for long-term management and storage of elemental mercurygenerated within the USA. This designation must occur no later than1 January 2010.
11.2.2 Mercury-containing and Rechargeable Battery
Management Act
The Mercury-containing and Rechargeable Battery Management Act of 1996(Battery Act) phases out the use of mercury in batteries and provides for theefficient and cost-effective collection and recycling, or proper disposal, of usednickel–cadmium batteries, small sealed lead–acid batteries and certain otherregulated batteries. The statute applies to battery and product manufacturers,battery waste handlers and certain battery and product importers and retailers.It phased out the use of mercury in batteries and established labeling, collectionand recycling and disposal requirements for certain regulated batteries.
11.2.3 Legislation Controlling Mercury Release
The Clean Air Act was introduced in 1970 and was amended in 1977 and 1990.Mercury was added as a hazardous air pollutant in 1990. The Clean Air Actregulates 188 air toxics, also known as ‘hazardous air pollutants.’ The Actdirects the US Environmental Protection Agency (EPA) to establish standardsfor certain sources that emit mercury. Those sources are also required to obtainClean Air Act operating permits and to comply with all applicable emissionstandards. The Act also establishes emission limits for sources of mercuryemissions, such as medical waste and solid waste incinerators, hazardous wastecombustors and chlor-alkali plants. The law includes special provisions fordealing with air toxics emitted from utilities, giving the EPA the authority toregulate power plant mercury emissions by establishing ‘performance stan-dards’ or ‘maximum achievable control technology’ (MACT), whichever theAgency deems most appropriate. MACT standards apply to both new andexisting sources of pollution.
Mercury generated by coal-burning power plants is regulated through the useof MACT standards.4 The Clean Air Act Amendments of 1977 and 1990contain an exemption that permits older coal-burning power plants to releasebetween four and ten times the amount of mercury that new plants may release.The stricter rules apply only to new or modified power plants.5
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The Clean Water Act of 1977 regulates the discharge of mercury into surfacewaters by using a permit system to regulate industrial discharges. Permits mayassign a facility a specific mercury discharge limit or require them to monitorand report on mercury discharges. The Clean Water Act authorizes the EPA toenact pollution control programs and set water quality standards for allcontaminants in surface waters.5 There is a bifurcation of standards under TitleIII of the Clean Water Act.5 Existing point sources of hazardous waste aresubject to the ‘best available technology’ (BAT). New point sources must abideby stricter ‘new source performance standards’ (NSPS). The permissiblemercury levels in 2004 for wastewater are given in Table 11.2.
The Comprehensive Environmental Response, Compensation and Liability Act(CERCLA), commonly known as Superfund, was enacted by Congress on 11December 1980. CERCLA requires that mercury spills of Z1 lb be reported tothe National Response Center. This law created a tax on the chemical andpetroleum industries and provided broad Federal authority to respond directlyto releases or threatened releases of hazardous substances that may endangerpublic health or the environment. CERCLA:
� established prohibitions and requirements concerning closed andabandoned hazardous waste sites
� provided for liability of persons responsible for releases of hazardouswaste at these sites and
� established a trust fund to provide for cleanup when no responsible partycould be identified.
CERCLA was amended by the Superfund Amendments and Reauthor-ization Act (SARA) on 17 October 1986.
The Superfund Amendments and Reauthorization Act (SARA) was imple-mented to provide funding for the clean-up of heavily polluted sites. Under theauthority of the Superfund Amendments and Reauthorization Act of 1986, theAgency for Toxic Substances and Disease Registry (ATSDR) works to preventor mitigate adverse human health effects and diminished quality of life resulting
Table 11.2 Clean Water Act effluent guidelines for one day.5
Type of wastewater BATa NSPSb
Smelter wet air pollution control 0.325mg troy oz–1 0.195mg troy oz–1
Silver chloride reduction, spent solution 0.010mg troy oz–1 0.060mg troy oz–1
Electrolytic cells, wet air pollution control 49.50mg troy oz–1 2.97mg troy oz–1
Electrolytic preparation wet air pollution control 0.013mg troy oz–1 0.008mg troy oz–1
Calciner wet air pollution control 46.55mgkg–1 3.30mgkg–1
Calciner quench water 4.40mgkg–1 2.640mg kg–1
Calciner stack gas contact cooling water 1.038mgkg–1 0.623mg kg–1
Condenser blowdown 3.45mgkg–1 2.07mgkg–1
Mercury cleaning bath water 0.35mgkg–1 0.21mgkg–1
aBAT¼best available technology.bNSPS¼new source performance standards.
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from exposure to hazardous substances in the environment. To do this,ATSDR provides expert support to Federal, State and local health officials.
The Resource Conservation and Recovery Act (RCRA) authorizes the EPA tocontrol all stages of the life cycle of hazardous waste. This includes hazardouswaste generation, transportation, storage and disposal. It also contains twoseparate regulatory pathways, one for new facilities and the other for oldfacilities. Older facilities are not required to meet all of the standards of newfacilities. The Resource Conservation and Recovery Act establishes disposalrequirements for wastes that contain mercury (e.g. thermometers, medical anddental wastes and mercury switches). It also allows States to adopt lessstringent ‘Universal Waste Rules’ if certain often-used, mercury-containingwastes are recycled (e.g. thermostats, fluorescent and high-intensity dischargelamps and batteries).
Under the RCRA, the EPA has specifically listed many chemical wastes ashazardous. Mercury is listed as a hazardous waste under the RCRA and hasbeen assigned EPA Hazardous Waste No. U151. This substance has beenbanned from land disposal until treated by retorting or roasting.
The RCRA requires that the EPA manage hazardous wastes, includingmercury wastes, from the time they are generated, through storage and trans-portation, to their ultimate treatment and disposal. The EPA has establishedtreatment and recycling standards that must be met before these wastes can bedisposed of. Certain mercury wastes – mercury-containing householdhazardous waste and waste generated in very small quantities – are exemptfrom some RCRA hazardous waste requirements. The RCRA also setsemission limits for mercury-containing hazardous waste that is combusted. USStates are largely responsible for implementing the RCRA program. IndividualStates may have stricter requirements than Federal requirements.
Under the Safe Drinking Water Act, the EPA sets standards for drinkingwater that apply to public water systems. These standards protect people bylimiting levels of mercury and other contaminants in drinking water. Mercurycontamination in drinking water can come from erosion of natural deposits ofmercury, discharges into water from refineries and factories and runoff fromlandfills and cropland. US States have the primary responsibility for enforcingdrinking water standards. The maximum contaminant level for mercury indrinking water, established under the Safe Drinking Water Act, is 0.002 mg L–1.
The Toxic Substances Control Act (TSCA) of 1976 provides the EPA with theauthority to require reporting, record-keeping and testing requirements, andalso to set restrictions relating to chemical substances and/or mixtures. Certainsubstances are generally excluded from TSCA, including food, drugs, cosmeticsand pesticides. The objective of the TSCA is to allow the EPA to regulate newcommercial chemicals before they enter the market, to regulate existingchemicals when they pose an unreasonable risk to health or to the environmentand to regulate their distribution and use.
The Emergency Planning and Community Right-to-Know Act forcesemployers who own or operate facilities in SIC codes 20–39 that employ 10 ormore workers and that manufacture 25 000 lb or more of mercury per calendar
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year, or otherwise use 10 000 lb or more of mercury per calendar year, arerequired by the EPA to submit a Toxic Chemical Release Inventory form(Form R) to the EPA reporting the amount of mercury emitted or releasedfrom their facility annually. In 1999, the limit for the amount of mercuryconsumed was lowered from 10 000 lb to 10 lbs. The Emergency Planning andCommunity Right-to-Know Act established three new regulations. It:
1. established reporting requirements for accidental and intentional releases2. established requirements to report inventory information to state and
local authorities3. required facilities to submit a report to the Toxics Release Inventory when
they manufacture, process or otherwise use 10 lb or more of mercury.
11.2.4 Food and Drug Administration
The US Food and Drug Administration (FDA) regulates the mercury contentin food, drugs and cosmetics. It limits the use of mercury as an antimicrobial orpreservative in cosmetics and regulates the use of mercury in dental amalgams.The Federal Food, Drug and Cosmetic Act (FFDCA) establishes an FDA actionlevel for methylmercury in fish at 1 ppm. The Food and Drug AdministrationModernization Act of 1997 (FDAMA), Amended 21 USC 301, required theFDA to compile a list of drugs and foods that contain intentionally introducedmercury compounds and to provide a quantitative and qualitative analysis ofthe mercury compounds in the list.
In 1999, the FDA undertook what they considered to be a comprehensivereview of the use of thimerosal in childhood vaccines. Although they found noevidence of harm, they did find that some infants could be exposed to cumu-lative levels of mercury that exceeded the EPA’s guidelines for safe intake ofmethylmercury.
Limitations on mercury-added products have been specified in regulationsgiven in the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA). Theobjective of FIFRA is to provide Federal control of pesticide distribution, saleand use. All pesticides used in the USA must be registered (licensed) by theEPA. Registration assures that pesticides will be properly labeled and that, ifused in accordance with specifications, they will not cause unreasonable harmto the environment. The use of each registered pesticide must be consistent withuse directions contained on the label or labeling.
11.3 Mercury Regulations and Standards
In October 2007, the EPA issued a Significant New Use Rule (SNUR) to requirenotification to the EPA 90 days prior to US manufacture, import or processingof elemental mercury for use in convenience light switches, anti-lock brakesystem switches and active ride control system switches in certain motorvehicles. In July 2010, the EPA issued a final SNUR for elemental mercury usedin flow meters, natural gas manometers and pyrometers. The Agency requires
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90 days’ notice prior to US manufacture, import or processing of elementalmercury for use in flow meters, natural gas manometers and pyrometers. TheRule is promulgated under Section 5(a)(2) of the Toxic Substances Control Actfor elemental mercury.
11.3.1 Measurement of Mercury in Water
Method 1631 allows for the determination of mercury at a minimum level of 0.5ppt and supports measurements for mercury published in the National ToxicsRule and in the Final Water Quality Guidance for the Great Lakes System.Revision E of the directive replaces the currently approved version of Method1631 and Method 1631 Revision C. This revision clarifies quality control andsample handling requirements and allows flexibility to incorporate additionalavailable technologies. This rule also amends the requirements regardingpreservation, storage and holding time for very low-concentration mercurysamples.
The Total Maximum Daily Load (TMDL) Regulations and Guidancegave the EPA’s regulations and guidance for the Total Maximum Daily Load,i.e. the maximum amount of a pollutant (including mercury) that a waterbodycan receive and still meet water quality standards.
11.3.2 Land Disposal Restrictions
The primary goal of the Resource Conservation and Recovery Act (RCRA)Subtitle C program is to protect human health and the environment from thedangers associated with generation, transportation, treatment, storage anddisposal of hazardous waste. Land disposal restrictions (LDRs) provide asecond measure of protection from threats posed by hazardous waste disposal.The LDR program ensures that hazardous waste cannot be placed on the landuntil the waste meets specific treatment standards to reduce the mobility ortoxicity of the hazardous constituents in the waste.
The LDR program found in 40 CFR Part 268 requires waste handlers totreat hazardous waste or meet specified levels for hazardous constituents beforedisposing of the waste on the land. This is called the disposal prohibition. Toensure proper treatment, the EPA establishes a treatment standard for eachtype of hazardous waste. The EPA lists these treatment standards in Part 268,Subpart D.
For non-wastewaters, the waste handler prepares an extract that reflects theleaching potential of hazardous constituents in the waste. The waste meets thetreatment standard if the concentration of regulated constituents in the liquidextract falls below the regulatory levels given for the waste code.
11.3.3 Mercury in Air
Reduction of Toxic Air Emissions from Industrial, Commercial and InstitutionalBoilers and Process Heaters Final Rule reduces toxic air pollutants, includingmercury, from industrial, commercial and institutional boilers and process
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heaters. This rule limits the amount of air toxics that may be released fromexhaust stacks of all new (built after 13 January 2003) and existing large andlimited-use solid-fuel boilers and process heaters located at facilities that areconsidered to be major sources of air toxics.
On 19 December 2003, the EPA introduced the Reduction of Toxic AirPollutants from Mercury Cell Chlor-Alkali Plants Final Rule. This Final Rulereduces mercury emissions from mercury cell chlor-alkali plants that areconsidered ‘major sources’ of hazardous air pollutants and also facilitiesconsidered to be ‘area sources.’ Mercury cell chlor-alkali plants producechlorine and caustic using mercury cells. A detailed discussion of chlor-alkaliplant operation is given in Chapter 9.
In April 2004, the EPA issued a regulation to control emissions from ironand steel foundries. The rule included emission limits for manufacturingprocesses and pollution prevention-based requirements to reduce air toxicsfrom furnace charge materials and coating/binder formulations. The rule alsoincluded a work practice requirement to ensure removal of mercury switchesfrom automobile scrap.
On 28 December 2007, the EPA issued a final National Emission Standardsfor Hazardous Air Pollutants (NESHAP) rule for electric arc furnace steel-making facilities. This Final Rule established requirements for the control ofmercury emissions that are based on the maximum achievable control tech-nology and requirements for the control of other hazardous air pollutants thatare based on generally available control technology or management practices.The final amendments to the NESHAP add or revise, as applicable, emissionlimits for mercury, total hydrocarbons (THCs) and particulate matter (PM)from new and existing kilns located at major and area sources and forhydrochloric acid from new and existing kilns located at major sources. Thestandards for new kilns apply to facilities that commenced construction,modification or reconstruction after 6 May 2009.
In August 2010, the EPA established the first regulations for mercuryemissions from cement factories. The production of Portland cement is believedto account for 7% of US mercury emissions. Mercury is emitted when cementcomponents such as clay, limestone and shale are heated in a kiln.
In December 2010, the EPA issued final regulations and added gold mine oreprocessing and production area to the list of source categories to be regulatedunder Section 112(c)(6) of the Clean Air Act. This source category was addedbecause of its significant mercury emissions. Gold ore processing was believedto be the seventh largest source of mercury air emission in the USA.
In February 2011, the EPA established practical and protective Clean Air Actemissions standards for large and small boilers and incinerators that burn solidwaste and sewage sludge. These standards cover more than 200 000 boilers andincinerators that emit harmful air pollutants, including mercury, cadmium andparticle pollution. The EPA also announced that it will reconsider certain aspectsof the boiler and commercial/industrial solid waste incinerator (CISWI) rules.
In July 2011, the EPA finalized the Cross-State Air Pollution Rule (CSAPR).The CSAPR requires States to improve air quality significantly by reducing
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power plant emissions that contribute to ozone and/or fine particle pollution inother States. This rule replaces EPA’s 2005 Clean Air Interstate Rule (CAIR).A December 2008 court decision kept the requirements of CAIR in placetemporarily but directed the EPA to issue a new rule to implement Clean AirAct requirements concerning the transport of air pollution across Stateboundaries. This action responds to the court’s concerns. The CSAPR aims toimprove air quality throughout the eastern half of the USA, helping Statesachieve national clean air standards. The emission reductions expected from theEPA’s recently finalized Mercury and Air Toxics Standards (MATS) are notincluded in the estimated emission reductions from the CSAPR.
In December 2011, the EPA, under the authority of the Clean Air Act, signedthe Mercury and Air Toxics Standards (MATS). The purpose of MATS was toreduce emissions of toxic air pollutants from power plants and set performancestandards for fossil fuel-fired electric utility, industrial–commercial–institutional and small industrial–commercial–institutional steam-generatingunits. Specifically, these mercury and air toxics standards for power plants willreduce emissions from new and existing coal- and oil-fired electric utility steam-generating units. MATS will reduce emissions of heavy metals, includingmercury, arsenic, chromium and nickel. The new law will also reduce emissionsof acid gases, including hydrochloric acid and hydrofluoric acid.
11.4 Occupational Safety and Health Administration
In 1974, the Occupational Safety and Health Administration (OSHA) set apermissible exposure limit for mercury in workplace settings at 0.1mgm–3 as anupper limit. OSHA’s revised Respiratory Protection Standard (29 CFR1910.134 and 29 CFR 1926.103) came into effect on 8 April 1998. The finalstandard replaces the respiratory protection standards adopted by OSHAin 1971.
Respirators are needed by people working with mercury. To comply with theOSHA Respiratory Protection Standard, employers should institute a completerespiratory protection program that, at a minimum, complies with therequirements of OSHA’s Respiratory Protection Standard. Such a programmustinclude respirator selection, an evaluation of the worker’s ability to perform thework while wearing a respirator, the regular training of personnel, respirator fittesting, periodic workplace monitoring and regular respirator maintenance,inspection and cleaning. A medical surveillance program must also instituted.A workplace respirator protection program is discussed in Chapter 14.
11.5 Department of Transportation and International
Air Transport Association
The transportation of mercury and mercury devices is covered by hazardousmaterials regulations under the Department of Transportation (DOT) andInternational Air Transport Association (IATA). These agencies require a
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hazardous material warning label for all air shipments regardless of the amountof mercury and for land freight in amounts of 1 lb or more.
References
1. N. Emmott and M. Slayne, in Dynamics of Mercury Pollution on Regionaland Global Scales, ed. N. Pirrone and K. R. Mahaffey, Springer, New York,2005.
2. EPA, Mercury: Laws and Regulations, 2012, http://www.epa.gov/hg/regs.htm (last accessed 9 March 2013).
3. EPA, Report to Congress: Potential Export of Mercury Compounds from theUnited States for Conversion to Elemental Mercury, 2009, http://www.epa.gov/hg/pdfs/mercury-rpt-to-congress.pdf (last accessed 9 March 2013).
4. M. Sweeney, MS Thesis, Massachusetts Institute of Technology, 2006.5. W. Thomas, Columbia J. Environ. Law, 2004, 29, 156.
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CHAPTER 12
Environmental Aspects of theIndustrial Application ofMercury
LEONID F. KOZIN,a STEVE C. HANSEN,b
NIKOLAI F. ZAKHARCHENKOa AND JASON GRAYc
aV. I. Vernadsky Institute of General and Inorganic Chemistry, NationalAcademy of Sciences of Ukraine, Kiev, Ukraine; b Consultant; cNipponInstruments North America, College Station, TX, USA
12.1 History and Uses of Mercury
Mercury has been used and is still used commercially despite its high toxicity.Mercury has valuable physicochemical properties and has been known forabout 2000 years.1 The properties of mercury have been described by Aristotle,Pliny the Elder, Paracelsus, Theophrastus, Vitruvius and Dioscorides. Ancientpeople made extensive use of the medicinal properties of some inorganicmercury compounds. For example, yellow mercury(II) oxide was used then as acomponent of eye and skin ointments. Mercury(II) chloride (HgCl2) has beenused as a strong disinfectant in medicine and as a fungicide in agriculture.Calomel (Hg2Cl2) has been used in medicine, in pyrotechnics and as a catalyst.Thiomersal is mainly used as an antiseptic and antifungal agent in medicinesand vaccines.
In the sixteenth century, Paracelsus (1493–1541), a Swiss doctor and naturalscientist, created pharmaceutical chemistry.2 Paracelsus struggled to obtain thepurest possible compounds of mercury, arsenic, copper, lead and silver andused small doses of them as medicines for various diseases. Before Paracelsus,
Mercury Handbook: Chemistry, Applications and Environmental Impact
By Leonid F Kozin and Steve Hansen
r L F Kozin and S C Hansen 2013
Published by the Royal Society of Chemistry, www.rsc.org
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mercury formulas were mostly used as extremely strong poisons. The lethaloutcome depended on the concentration of mercury administered to thehuman body.
Mercury has been used to produce ship fouling-prevention paints forseawater1,3 and other paints. In agriculture, mercury is a long-establishedcomponent of pesticides.1,3,4 Mercury is used in micro- and optoelectronics,5
the electrical engineering industry,6,7 the instrument-making industry,8
discharge lighting (see Chapter 7), technical electrochemistry in theproduction of chlorine and alkali (see Chapter 9), electrosynthesis of organo-mercury compounds,9 amalgam metallurgy (production of highly refinedmetals),10–13 aluminum14 and gold production,15–19 stripping voltammetry,20,21
medicine for dental amalgams based on mercury, tin and silver, polarographywith mercury electrodes,22–25 inorganic synthesis of sodium sulfide andhydrosulfite,26 organometallic synthesis and other products.1,27,28
Solvent extraction of mercury from chloride media29 is in common use.Mercury oxide has recently gained prominence as a key component of high-Tc
superconductors.30 Among the most widely used technologies is the growth ofepitaxial films Hg1–xCdxTe
31 (see Chapter 8), colloidal nanocrystals of HgTe32
and the production of complex epitaxial heterostructures. These structures arebased on cadmium–mercury–tellurium solid solutions viametallorganic chemicalvapor deposition over carriers of gallium arsenide,33 indium phosphide, etc.
This chapter discusses the occurrence of mercury in Nature and its physi-cochemical and thermodynamic properties in the mercury–water system. It alsodemonstrates that mercury belongs to hazard class I and is toxic for humansand warm-blooded animals. The discussion addresses the maximum allowableconcentrations (MACs) of inorganic and organic mercury compounds in waterand air – including potable water and effluents – the mechanisms of trans-forming mercury from inorganic to organic compounds by the action ofanaerobic and aerobic bacteria and microorganisms and mercury circulationcycles within the Earth’s ecosystem. A method to measure atmospheric mercuryis briefly discussed.
12.2 Occurrence of Mercury in Nature
Mercury is a trace element, its average content in the Earth’s crust being7�10–6wt% (0.5 g t–1).1,34 Mercury’s geochemical Clarke value is 7�10–7 wt%(0.007 g t–1) and its industrial Clarke value is 4.2�10–4 wt%,35 i.e. 600 timeshigher, which is an indication of the extensive use of mercury in industry, tech-nology and science.1
Global reserves of mercury total about 600 000 t. It is believed that only0.02% of mercury reserves are concentrated in deposits of hydrothermal origin.There is a registered total of 324 000 t of mercury in deposits in Spain (whichaccounts for 26% of the total), Russia (14%), Kirghizia (Kirghizstan) (13%)and Ukraine – Nikitovka (8%). Among the other countries that hold significantportions of the total reserves are the USA, Mexico, Turkey, China andSlovenia.
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While the mineral reserve base of the global mercury industry is adequate tosatisfy the global demand quantity wise, its quality characteristics are notcompletely satisfactory. The highest quality ores with an average metal contentabove 1.5% are found only in Spain and Algeria. In all other countries themercury ore is at least three times less rich, which makes it very difficult toachieve cost-effective production given the current prices. Moreover, mostmercury deposits contain relatively moderate reserves of the metal. Out ofaround 2000 of the world’s mercury deposits (1000 of which were mined atdifferent periods), only seven – Almaden, El Entredicho and Las NuevaConcepcion (Spain), Fendek (Algeria), Wanshan and Danchjai (China) andKhaidarkan (Kirghizia) – contain large reserves, together accounting for 80%of world reserves.
Cinnabar (HgS) is the most widely distributed mercury mineral and themost stable natural mercury compound. Mercury is also found in a wide rangeof complex minerals and complementary polymetallic ores.36 There are 35known mercury-containing minerals, some of which are listed in Table 12.1.Mercury complements copper-, arsenic-, antimony-, lead-, thallium- andselenium–tellurium-bearing ores. Mercury ores are categorized as rich(containing B1 wt% or more Hg), common (0.2–0.3wt% Hg) and lean(0.06–0.12wt% Hg).
12.3 Recovery of Mercury from HgS
Pyrometallurgical and hydrometallurgical processes are used to producemercury. In the pyrometallurgical process, ore or mercury concentrates are
Table 12.1 Mercury-bearing ores.36
Name Ore Hg (at.%) Hg (wt%)
Velikite Cu2HgSnS4 12.5 34.9Galkhaite Tl(Cu,Hg,Zn)12As8S24 0–26.6 0–60.5Temagamite Pd3HgTe3 14.2 22.2Atenaite (Pd,Hg)3As 0–75 88.9Khakite (Cu,Hg)3SbSe3 0–42.3 0–62.9Balkanite Ag5Cu9HgS8 4.3 12.8Saukovite (Hg,Zn)S 0–50.0 0–86.2Timanite HgSe 50.0 71.8Lorodaite HgTe 50.0 61.1Korderoite a-Hg3S2Cl2 42.3 81.7Petrovicite Cu3PbHgBiSe5 9.1 16.7Gruzdevite Cu6Hg3Sb4S12 11.5 32.4Aktashite Cu6Hg3As5S12 11.5 34.5Livingstonite HgSb4S8 7.7 21.3Tvalchrelidzeite Hg12(Sb,As)8S15 34.2 69.0Christite TlHgAsS3 16.6 34.8Laffittite AgHgAsS3 16.6 41.8
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roasted at 673–1173K in fluidized-bed furnaces. Elemental mercury isproduced through the following reactions:
HgS! Hgþ 1=2S2 ð12:1Þ
MeiðHgMejÞSn ! HgþMeiMejSn�1=2 þ 1=2S2 ð12:2Þ
When mercury undergoes one of these reactions, it evaporates and condensesinside special chambers where it is collected and purified by either physico-chemical or electrochemical methods1 (see Chapter 4). Reactions 12.3 and 12.4show the oxidation of the non-mercury metals present in the mercury-bearing ore:
MeiMejSn�1=2 þ ðnþmÞO2 !MeiOn þMejOm ð12:3Þ
1=2S2 þO2 ! SO2 ð12:4Þ
In hydrometallurgical processes, cinnabar contained in concentrates and oresis leached with the help of ligands (Cl–, Br–, etc.) and the resulting solutions aresubjected to electrolysis, electrolytic precipitation, hydrolytic reprecipitation,etc. Hydrometallurgical processes recover only B90–95% of mercury fromores and concentrates. Open sludge dumps that build up around mercuryproduction facilities are permanent sources of mercury vapor.
Polymetallic sulfide ores contain from 10–4–10–2 up to 1.0–2.5 wt% ofmercury. In the course of polymetallic ore processing, mercury, being a metallicimpurity, is normally not extracted but instead is distributed between the endproducts and often concentrates into one of them. Being highly volatile(the metallic mercury content at 0, 20 and 100 1C is 2.0, 14.0 and 242 g dm–3 ofair, respectively) and easily restorable in the course of pyrometallurgicalprocessing of ore or concentrate, mercury mostly disperses in the environment,which, as shown below, creates a lethal hazard for humans and warm-bloodedanimals4,37–39
As noted above, mercury and mercury-based compounds have been knownsince ancient times. In the five centuries before 1925, the world producedaround 106 t of metallic mercury, which was mostly used for the production ofgold and silver.40 It should be noted that 106 t of metallic mercury has, over theyears, already been dispersed in the environment. Metallic mercury and its ions
(Hg2þ2 , Hg21) and hydroxo and other compounds of varying complexity are
formed from ore deposits in which mercury is contained in the form of theabove-mentioned minerals, by atmospheric and hydroerosive processes andredox reactions.
12.4 Amounts of Mercury Used in Industry
As noted above, the world’s geological reserves of mercury are currentlyestimated at 600 000 t and global reserves of mercury make up 209 200 t.41
Estimates of mercury use throughout the 1980s are given in Table 12.2.42
Therefore, it is assumed that global reserves will last at least 85–90 years.
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However, world production of mercury has begun to fall rapidly. According tothe US Geological Survey, mercury extraction in 1997 was 3447 t and in2006–2007 was only 1500 t.43 The main reason for the sharp reduction inmercury extraction and the reduced demand for it at the end of the twentiethcentury was the realization that mercury and its compounds are highly toxic,causing increasing damage to ecological areas of human habitation.
In recent years, China has been supplying B70–75% of world mercuryextraction. Kirghizia, the world’s second largest producer, extracted 200–300 tof mercury annually. Total mercury extraction in other countries is 100–150 tper year, although not in the form of a commercial product. For manycountries the main source of mercury can be recycled mercury and unclaimedmercury reserves in mine waste piles and slurry pits. Mercury from secondarysources, such as dental amalgam, fluorescent lamps, thermostats, fossil-fueledelectric power stations, car switches, batteries, emissions from cement plantsand metallurgical refineries, PVC production and artisanal and small-scale goldmining,43–45 account for much of the mercury used in commerce.
For example, in the USA, recycled waste furnishes 29% of the mercuryconsumed.41 In 1970, the US population had more than 150millionmercury–silver amalgam dental fillings installed. The noted reduction inmercury consumption over time is associated with decreased productionof mercury batteries, paints, chlor-alkali plants and dental amalgams andreduced amounts of mercury in fluorescent lamps, pesticides, insecticides, etc.From 1950 to 1980, the Nikitovsky Mercury Plant in Ukraine produced about800 tons of mercury for the USSR gold industry; from 1981 to 1991 theextraction of mercury was reduced to 400 tons per year, but the production ofhigh-purity mercury 99.99999–99.999999 (7N–8N) wt% for the semiconductorindustry was 5–8 tons per year. After about 1992, mining of mercury in theNikitovsky mercury plant in Ukraine was reduced to 50 t per year or less.
The USA is an importer of mercury (importing between 131 and 696 t peryear). Domestic production in the USA, which amounted to 577.1 tin 1985 and416.5 t in 1986, did not satisfy the country’s demand for this metal.6 Theproduction of secondary (recycled or reclaimed) mercury rose steadily up to1988, as follows:
1985 185 t1986 219 t1987 265 t1988 278 t
Table 12.2 Mercury use during the 1980s.
Year Hg usage (t)42a Hg usage (t)42b
1980 9244 68181984 6909 60361987 7255 59061988 7866 –
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The current task s to demercurize emissions sufficiently from the following:sulfur production, Waelz kiln production of zinc,1,46 aqueous solutions ofacids,1,47–53 chlor-alkali production,1,54–59 aqueous solutions and solutions ofalkalis and hydrosulfides with sulfur.1,47–53,60–63 The following processes arecurrently under development: sorption methods to extract mercury ions fromsolution,49,64–67 methods of mercury extraction from solutions using liquidmembranes,68 using anion-exchange resins,69–73 extraction of mercury byelectrolysis1,74–77 and electrolytic precipitation,78,79 radiochemical80 andbiological purification81 and mercury sulfide precipitation.82,83
12.5 The Role of Industry in Environmental Mercury
Pollution
Metallic mercury has a relatively high vapor pressure at ambient temperatureand low heats of fusion and vaporization. Therefore, metallic mercury easilyevaporates into the atmosphere and is dispersed around the planet with airmasses and precipitation. Metallic mercury also partly dissolves in environ-mental waters. Figure 12.1 illustrates the exchange equilibrium between air andwater, which is in a complex functional relationship with many factors(temperature, vapor and gas pressure, concentration of salts in water, etc.).Figure 12.2 summarizes data1,6 on the solubility of metallic mercury water inrelation to temperature (273–773K).1,84
Figure 12.1 Mercury circulation within the Earth’s ecosystem.Source: US EPA.114
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As can be seen in Figure 5.1, in the temperature range 273–500K, thesolubility of metallic mercury is directly proportional to temperature. Attemperatures 4500K (marked with an arrow) the curve deviates from thelinear lnm–T relation. The solubility of metallic mercury in water, expressed inmole fractions (x Hg), is described by the equation84
log xHg¼� 147:56þ 5581:3=T þ 48:7231 logT ð12:5Þ
where T is the temperature (K). It has been reported that the solubility ofmetallic mercury in water is (3.0� 0.1)�10–7mol dm–3 (0.602mgL–1) at298K.85 It has been determined that the solubility of metallic mercury in waterdecreases in the presence of salts of inorganic compounds.1 A systematicanalysis of the solubility of metallic mercury in aqueous solutions of elec-trolytes (NaCl, NaOH) has been performed.86–89
Figure 2.1 also illustrates that mercury enters water as a result of industrialactivities and ablation from the Earth’s crust. Mercury minerals demonstrate acertain, albeit low, solubility in water. The solubility product of mercury sulfideis small and equal to 2�10–49 at 283K,3 while the solubility at 291K is1.25�10–6%.90 The solubility products of HgS, HgSe and HgTe91 decrease inthat order, with values of 1.4�10–45, 2.4�10–61 and 1.0�10–64, respectively.Thus, the solubility of mercury in water decreases with the transition fromsulfides to tellurides. Therefore, being a trace element, mercury is omnipresentunder natural conditions but its concentrations are normally very low. It hasbeen established that in Nature inorganic forms of mercury chalcogenides areconverted into metallic mercury under the action of enzymes of anaerobicbacteria:
HgSðSe;TeÞ"Hg2þ"Hg2þ2 "Hg0þS2�ðSe2�;Te2�Þ ð12:6Þ
It is also proven that divalent mercury ions are converted into metallic mercuryunder the action of Pseudomonas bacteria in aerobic conditions.92 The tran-sition of mercury chalcogenides into metallic mercury may also take place as aresult of electrochemical reactions, given a favorable mercury potential. Thereduction may occur as follows:
HgXþ 2e! Hg0 þX2� ð12:7Þ
where X2–¼ S2–, Se2–, Te2–. The opposite is also true, given the appropriateoxidation potential of mercury, as seen from the equation
E¼ 0:850þ RT
2Fln
Hg2þ� �
a
!ð12:8Þ
According to Jensen and Jernelov,92 mercury will dissolve if a is greaterthan 1021:
Hg0"Hg2þ þ 2e ð12:9Þ
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Redox reactions and aerobic/anaerobic bacteria result in the formation ofmetallic mercury and its inorganic and organic compounds, which circulate innature. Ultimately, up to 5000 t per year of metallic mercury and its compoundsare deposited by natural causes (volcanoes, etc.) into the oceans.
12.6 Mercury Pollution
In recent years, another 5000 t per year of mercury have been added to theabove amount as a result of anthropogenic (man-made) activities.3 Thesemercury ‘loss’ figures amount to half of the world’s industrial production ofmercury, which has reached between 5000 and 10 000 t per year.2,3,6,39,40
Mercury-based industrial processes involve huge losses of the metal.According to an estimate,3 the industrial production of chlorine and alkalialone has accounted for 106 t of mercury losses. For example, an elec-trochemical chlorine facility in Ontario lost 15 kg of mercury per day, whichadded up to 100 t of mercury lost over 20 years.3 In addition, the world’s oceanshave accumulated around 50�106 t of mercury as a consequence of erosion,underwater volcanic activity and anthropogenic activity. The concentration ofmercury in ocean water is 3�10–5mgL–1. Consequently, atmospheric andhydroerosive processes result in the ‘spreading’ of mercury over the planet. Dueto evaporation, mercury becomes airborne at a concentration of 20 ngm–3,which is equivalent to 20 ng cm–2 of the Earth’s surface.84 Natural mercuryconcentrations range from 3 to 9 ngm–3. Near mercury factories, concen-trations may reach 50mg cm–2 of the Earth’s surface.93 The airborne concen-tration of mercury over the Mazatzal Mountain pit in Arizona is 20 mgm–3.This mercury vapor concentration is far below the saturation limit.
In Chapter 1, we summarized data that measure the vapor pressure ofmercury. It was seen that vapor pressure increases exponentially with increasein temperature. The airborne concentration of mercury at room temperature atits saturation point lies in the range 10–15mgm–3. Such high airborneconcentrations of mercury occur only inside closed spaces, e.g. a laboratoryroom containing spilled or splashed mercury with a large evaporation area. Themaximum allowable airborne concentration of mercury accepted in mostcountries, including the USA, is 100 mgm–3, and in CIS countries it is 10 mgm–3
and for alkylmercury compounds 5 mgm–3.94,95 The maximum allowable meandaily airborne concentration of mercury in populated areas is 0.3 mgm–3.95
The mercury concentration in rain water was stated to be 200ngL–18 in onereport4 and 50–500ngL–1 in another.96 The mercury concentration in snow is0.07–0.21ngL–1,97 but in the vicinity of mercury facilities these snow concentrationlevels may be exceeded 100–1000-fold.97 Based on the average mercury content insnow and rain water, it was found that every year atmospheric precipitationenriched with mercury from various sources, including natural sources, depositaround 100000 t of mercury to the surface of the Earth.98 It should be notedthat burning fossil fuels containing considerable quantities of mercury (browncoals 2.5�10–6%, anthracites 2.7�10–4%, petroleum products 1.9–21.0�10–4%contributes substantially to mercury emissions into the atmosphere.3
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The oceans receive mercury mostly in the form of the Hg21 ion, which thenreacts with organic substances and anaerobic microorganisms to become thetoxic methylmercury (CH3Hg1) and dimethylmercury [(CH3)2Hg].3 It isprecisely the anaerobic and aerobic microorganisms that transform theinorganic mercury compounds into the extremely harmful organic mercurycompounds – methylmercury, dimethylmercury, etc. According to Stock andCucuel,96 ocean water has a mercury content of about 30 ngL–1. The mercurycontent in ocean water depends on depth. It is 60–240 ngL–1 at a depth of500m and 150–270 ngL–1 at 3000m.3 Methylmercury, just like dimethyl-mercury, easily dissolves in water and quickly infiltrates aquatic organisms.The mercury concentration in freshwater fish is 76–167 ng g–1, while fishfrom various sources in Sweden, Finland, Norway and Switzerland contain60–2500 ng g–1 of mercury.93 Notably, mercury contained in fish exhibitsbioaccumulation with an enrichment factor of 3000–9200.93 Ocean fish containless mercury. Mercury is also present in the meat of domestic grazing animals(sheep, cows, etc.) and fowl. Consequently, mercury enters the human bodythrough the food chain. The actual quantity of mercury entering the humanbody depends on the person’s living environment and the type of food. Themigration of mercury and its transport within the environment through water,air and plankton stimulated by industry and plants is illustrated in Figure 12.1.The mercury migration chain closes with humans. It is important to note that inthe hydrosphere the pollution effect is increased owing to the ability of thebiosphere to concentrate mercury and other microelements to thousands ormillions of times the levels of the surrounding water environment.
Ostroumov et al.99 studied the mercury content of clams in theocean ecosystems. They demonstrated that clams contain mercury at levels of133–217 ng g–1 of the dry weight of the soft tissue. As mussels grow older, themercury content increases to 2.0–5.8 mg g–1, i.e., 15–26-fold. The microgramlevels of mercury in mussels indicate the bioaccumulation effect demonstratedby organisms in the oceans. Owing to bioaccumulation, the natural levels ofmercury in some organisms are close to the threshold safety level of0.5�10–4%.3 Thus, commercially produced fish coming from near to industrialregions on average contain 0.5�10–4% of mercury, which is exactly thethreshold safety level. It has been demonstrated in the early 1980s that the highmercury content in sea fish had hardly changed over the past century:0.95�10–4% in the meat of tuna caught in 1878 and 1909 and 0.91�10–4% incommercial species caught in 1981.3 Therefore, the problem of mercurypoisoning depends not only on the mercury concentration in fish, but also onthe amount of fish consumed. The human body receives 20–50 mg of mercurydaily.100 According to Masters,6 the temporarily allowable total weekly dose is0.3 mg for mercury and 0.2 mg for methylmercury.3,4,101,102
12.7 Environmental Mercury
The release of mercury and its organic compounds into water basins, rivers andseas may lead to environmental disasters. From 1932 to 1968, the Chisso
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chemical plant, located on Kyushu island off the coast of Japan, dumped 600 tof mercury in the form of methylmercury and other organomercurycompounds into the Shiranui Sea andMinamata Bay, where it was absorbed byshellfish, plankton and microorganisms. These microorganisms were consumedby small fish, which in turn became food for larger fish. Thus the biologicalmercury transformation chain was transferred to humans, as shown inFigure 12.1. The high concentration of organic mercury compounds in thewaters of Minamata Bay and the Shiranui Sea led to high mercury contents infish and clams used for food by the local population, and the inhabitants ofKyushu Island were stricken by a formerly unknown disease dubbed‘Minamata disease.’ The victims suffered from disruption of the central nervoussystem, which presented itself variously as psychiatric disorders, even insanity,loss of coordination, loss of pain sensitivity, loss of hearing, eyesight and speechand convulsions leading to torpor and coma.3,4,82,100 Among the approximately2500 victims, the mortality rate was 32.8%.100
The health impact of metallic mercury is based on oxidation reactions
producing Hg2þ2 and Hg21 ions, which, in the presence of chlorine ions, take
part in exchange reactions leading to the production of calomel [mercury(I)chloride] and mercury(II) chloride. The toxicity of inorganic mercurycompounds depends on their solubility in water, blood and gastric juice. Owingto the high toxicity of mercury, according to the World Health Organization,the maximum allowable quantity of mercury consumed per person per daymust not exceed 0.3mg, including no more than 0.2mg of methylmercury.3
The total mass content of mercury in the human body is 1�10–6%.99
Symptoms of mercury poisoning occur at a body burden level of2–6�10–5%, which corresponds to 14.0–42.0 mg of mercury for an individualweighing 70 kg. Mercury is mostly concentrated in the kidneys and less so inthe liver.
The symptoms of Minamata disease correspond to the properties of themercury compounds. The action of mercury depends on the nature of itscompounds. Methylmercury administered into the body quickly enters thebloodstream and brain tissue, destroying the cerebellum and the brain cortexand thereby leading to a loss of spatial orientation and partial loss of eyesight.Inorganic mercury compounds are also highly toxic; however the effects oftoxicity depend on the nature of the mercury consumed. Prolonged inhalationof mercury vapor at a concentration of 0.6–2mgm–3 exposes the human bodyto a macro-concentration of mercury with a highly developed (at the molecularlevel of Hg2) surface, thereby leading to acute intoxication, which is a fore-runner of chronic poisoning. Acute mercury vapor poisoning is marked by adisturbance of calcium metabolism, modification of blood proteins andmercury accumulation in the liver, kidneys, brain and spleen, which in turnsuffer actual damage. Chapter 14 discusses the symptoms and effects of acutemetallic mercury poisoning in more detail.
Mercury is a material of hazard class I.82 The threshold concentrationof mercury affecting the functional capacity of the central nervous system is
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2–5mg–3,96 while the maximum allowable mean daily airborne concentration ofmercury for populated areas is 0.3mgm–3.98 The mercury MAC for potablewater is 0.001mg-L–1 according to international standards, 0.002mg-L–1
according to US standards and 0.005mgL–1 for utility facilities.82 Japaneselaw allows no mercury content in domestic potable water reservoirs orwastewater. European standards limit the mercury concentration in potablewater to 0.01mgL–1.82
Nevertheless, despite centuries of accumulated knowledge about the toxiceffect of mercury and its compounds on warm-blooded animals and humans,the environmental issue of mercury control and pollution prevention was firstaddressed only in the 1950s and escalated in 1984–2007.6,46,54–59,103–108
The following factors are of extreme importance: promotion of industrial useof recycled mercury, improving the culture of handling mercury-containingdevices (medical thermometers, technical thermometers, electrochemicalbatteries, fluorescent lamps, etc.) in households and the development of greentechnologies for both the production and utilization of mercury in industry,agriculture, science and medicine.6,46,54–59,103–108
12.8 Mercury Detection by Atomic Fluorescence
Spectrometry
Many methods of mercury detection are now available.109 Of the manyanalytical methods available, cold vapor atomic absorption spectrometry(CVAAS), inductively coupled plasma mass spectrometry (ICP-MS),plasma atomic emission spectrometry (plasma AES) and cold vapor atomicfluorescence spectrometry (CVAFS) are in widespread use. They can beused to determine mercury in water at the picogram level. CVAAS hasdetection limits of 0.01–1 ng g–1, ICP-MS 0.01 ng g–1 and CVAFS0.001–0.01 ng g–1.109,110 A brief description of atomic fluorescence spec-trometry (AFS) is given below.
12.8.1 Atomic Fluorescence Spectrometry
One of the most sensitive methods for measuring environmental mercury isAFS. With this technique, it is possible, with appropriate preparative methods,to measure mercury in water, soil and air. With cold vapor preconcentration ofmercury, CVAFS is a well-known analytical method where manyimprovements have been made to automate and improve the sensitivity andlimit of detection. One advantage of AFS over atomic absorption spectrometry(AAS) is the ability to use more intense light sources. AFS has a larger lineardynamic range, higher sensitivity and less interference than AAS.111 Of thesetwo methods, CVAFS is the more sensitive. The fundamentals of AFS havebeen reviewed by Morita et al.112
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12.8.2 Application of CVAFS for the Determination of Mercury
in Water
CVAFS is a widely used and powerful analytical method capable of measuringmercury in water at levels of o10–9 g L–1 (o1 ngL–1). To be successful, themethod described below requires significant skill, particularly with samplecollection and handling. Mercury determination, according to US EPAMethod 1631E,113 focuses on monitoring waste effluents at the lowest EPAWater Quality Certification (WQC) levels. Method 1631E has a prescribedanalytical range for mercury of 0.5 ng L–1–100 ngL–1.
Samples are first oxidized using a solution of bromine monochloride (BrCl)in order to liberate and transform the mercury present into its inorganic(Hg21), water-soluble form. Once the samples have been completely oxidized,they are then treated with hydroxylamine hydrochloride (NH2OH�HCl), a mildreducing agent, to destroy free halogens. Samples are then further reduced withstannous chloride solution (SnCl2), which transforms mercury into itselemental and volatile state that can be easily removed from solution. Theelemental mercury is transferred to the gaseous phase and is then collected on agold trap to isolate and concentrate the mercury. Subsequently, the gold trap isheated to liberate elemental mercury and the mercury is transferred through anoptical cell for detection via AFS.
Figure 12.2 shows a schematic diagram of an older CVAFS system without themanual purging apparatus, taken from EPAMethod 1631E.113 The lamp in older
Figure 12.2 Schematic diagram of the manual AFS analyzer without the manualpurging apparatus.Reproduced with permission from Ref. 113.
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systems would have emitted a diffuse spectrum and so an interference filter wasneeded to limit the light source to 254 nm radiation. In more modern systems, amercury discharge lamp is used since it has a narrow emission spectrum around254nm. The chart recorder output gives time on the x-axis and absorbance on they-axis. In modern systems, software is used instead of a chart recorder, but theoutput will still be a similar portrayal of absorbance versus time. The part labeled‘Sample Trap’ is a gold trap used to collect mercury from the aqueous sample.The sample is purged to get the mercury out of solution and on to the gold trap.This trap is then placed in the analyzer, where it is heated to release the mercuryon to the part labeled ‘Analytical Trap’. The ‘Analytical Trap’ is a second goldtrap that is then heated to release the mercury for analysis. In this setup, the firstgold trap can be one of multiple different gold traps for multiple samples, eachcollected on a different trap. All samples are desorbed on analytical traps.Multiple gold traps help increase the consistency from sample to sample.
Figure 12.3 shows the peak responses for a typical calibration curve.Table 12.3 shows typical quality control figures for calibration data that were
Sample No.
Inte
nsity
1 2 3 4 5 6 7
0
10
20
30
Figure 12.3 Calibration peaks from blank to 50 ppt Hg for mercury determination inwater. Courtesy of Nippon Instruments North America.
Table 12.3 Typical control chart from data collected on a commercial AFSinstrument.
No. Quality control checksa Acceptance criteria Result Pass
1 Bubbler blank average 0.5 ng L–1 0.093 ng L–1 OK2 Bubbler blank standard deviation 0.1 ng L–1 0.012 ng L–1 OK3 Calibration factor RSD 15% 2.56% OK4 Calibration factor recovery 75–125% 100.49% OK6 Method blank 0.5 ng L–1 0.137 ng L–1 OK7 OPR 77–123% 107.10% OK
aRSD, relative standard deviation; OPR, ongoing precision and recovery.
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collected on a commercial instrument. Substances that produce very stablecomplexes with mercury ions may interfere with the reduction of the ions to theelemental form. Complexes of bromides, iodides, cysteine and sulfide, thio-sulfate and Se(IV) have been reported to cause interference112 in the deter-mination of mercury by CVAFS unless they are decomposed before reduction.
References
1. L. F. Kozin, Physicochemistry and Metallurgy of High-Purity Mercuryand Its Alloys, Naukova Dumka, Kiev, 1992.
2. V. Shtrube, Avenues for Development of Chemistry, Mir, Moscow, 1984,vol. 1.
3. J. O’M Bockris (ed.), Environmental Chemistry, Springer US, 1977,pp. 1–18.
4. I. M. Trachtenberg and M. N. Korshun, Mercury and Its Compounds inthe Environment, Vysha Shkola, Kiev, 1990.
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6. H. B. Masters, Metals and Mining Annual Review 1997, Mercury. MiningJ. Ltd., 1997.
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Analysis, Goskhimizdat, Moscow, 1959.25. A. M. Bond, Polarographic Methods in Analytical Chemistry, Khimiya,
Moscow, 1983.26. Jpn. Ind. Chem. Soc., 1965, 68, 1248.27. H. Lund and O. Hammerich (eds), Organic Electrochemistry, 4th edn,
Marcel Dekker, New York, 2001.28. A. M. Bond, R. T. Gettar and N. M. McLachiam, Inorg. Chim. Acta,
1989, 166, 279.29. M. F. Francine and B. M. Marcelo, Hydrometallurgy, 2007, 87, 83.30. J. Wu and H. Zhao, in High Temperature Superconductors,
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environment: emissions into the atmosphere, restoration of territories,impact on health, in Proceedings of the International Seminar, Astana, 28May–1 June 2007, Abstracts, 2007, pp. 18–19.
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I. A. Sheka, Ukr. Khim. Zh., 1974, 40, 364.50. G. B. Budkevich, V. Y. Momot, I. I. Sirenko and Y. A. Tarasenko,
Method for mercury removal from solutions, USSR Pat., 1972, 382 720.51. Mercury removal from sulfuric acid solutions, Jpn. Pat. Appl., 56-48588.52. Removing mercury from concentrated sulfuric acid solutions, Jpn. Pat.
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62. J. Markovs, R. T. Maurer, A. S. Zarchy and E. S. Holmes, US Pat., 5 354357, 1994.
63. Russian Federation Patent 2,327,536 Method for disposal of mercury-containing wastes.
64. C. R. Palmer and R. G. Sandberg, Precious Metals: Mining, Extractionand Processing, Proceedings of International Symposium, AIME AnnualMeeting, Los Angeles, California, 27–29 February 1984, TMS,Warrendale, PA, 1984, pp. 227–239.
65. Mercury sorbent recovery, Fr. Pat. Appl., 2 615 756.66. R. G. Sandberg, US Bureau of Mines Circular, No. 9059, US Department
of the Interior, Washington, DC, 1986, pp. 19–25.67. V. F. Kamenev and L. V. Fadeeva, Tsvet. Met., 1985, 10, 49.68. K. Inoue, Y. Bada M. Goto, et al., in Proceedings of the First International
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69. I. Dodreusky, A. Dimin, V. Nenov, et al., in Proceedings of the FirstInternational Conference on Hydrometallurgy, Beijing, 1988, ICHM 88,Beijing, Oxford, 1989, p. 666.
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74. M. W. Grossman and W. A. George, US Pat., 4 879 010, 1989.75. S. P. Kounaves and J. Buffle, J. Electrochem. Soc., 1986, 133, 245.76. Method for mercury recovery from solutions, USSR Pat., 1 668 483.77. B. P. Giri, US Pat., 6 221 128, 2001.78. D. L. Ball and D. A. D. Baoteng, US Pat., 5 013 358, 1991.79. Method for mercury recovery, USSR Pat., 195 112.80. A. V. Malkov, N. P. Tarasov and J. Belloni, All-Union Conference on
Theoretical and Applied Radiation Chemistry, Obninsk, 23–25 October1990, Abstracts of Reports, Moscow, 1990, pp. 184–185.
81. M. E. Goldstone, C. Atkinson, P. W. W. Kirk and J. N. Lester, Sci. TotalEnviron., 1990, 95, 271.
82. M. Ya. Grushko, Harmful Inorganic Compounds in Industrial Effluents,Khimiya, Leningrad, 1979, p. 160.
83. G. E. Kislinskaya and L. I. Fedoryako, Khim. Tekhnol., 1989, 2, 23.84. M. Iwamoto, S. N. Jonson and H. Miyamoto, Mercury in Liquids
Compressed Gases, Molten Salts and Other Elements, Solubility DataSeries, ed. A. S. Kertes and H. L. Clever, Pergamon Press, New York,1986, vol. 29.
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87. A. A. Shokol and L. F. Kozin, Ukr. Khim. Zh., 1959, 25, 374.88. V. K. Chviruk and N. V. Koneva, Zh. Prikl. Khim., 1978, 51, 743–746,
747–751.89. V. K. Chviruk, N. V. Koneva and A. Yu. Noel’, Zh. Prikl. Khim., 1974,
47, 2546.90. F. G. Gavryuchenkov, M. I. Kurochkin, A. A. Potekhin and V. A.
Rabinovich, Chemistry Reference Book, translated from German,Khimiya, Leningrad, 1975. p. 576.
91. R. A. Lidin, L. L. Andreeva and V. A. Molochko, Constants of InorganicSubstances, Drofa, Moscow, 2006.
92. S. Jensen and A. Jernelov, Mercury Contamination in Man and HisEnvironment, Technical Report Series, No. 137, International AtomicEnergy Agency, Vienna, 1972, pp. 43–66.
93. A. V. Holden, Mercury Contamination in Man and His Environment,Technical Report Series, No. 137, International Atomic Energy Agency,Vienna, 1972, pp. 143–168.
94. N. V. Lazarev and I. D. Gadaskina (eds), Harmful Substances in Industry,Inorganic and Organoelement Compounds, Khimiya, Leningrad, 1977.
95. Ya. M. Grushko, Harmful Inorganic Compounds in Industrial Emissionsinto the Atmosphere, Khimiya, Leningrad, 1987.
96. A. Stock and F. Cucuel, Naturwissenschaften, 1934, 6, 390.97. V. N. Kumok, O. M. Kuleshova and L. A. Karabin, Solubility Products,
Nauka, Siberian Branch, Novosibirsk, 1983, p. 266.98. F. P. W. Winteringham, Mercury Contamination in Man and His
Environment, Technical Report Series, No. 137, International AtomicEnergy Agency, Vienna, 1972, pp. 1–3.
99. S. A. Ostroumov, S. D. Hushkhvatova, V. N. Danilov andV. V. Ermakov, Environ. Chem., 2008, 17, 84.
100. V. G. Huhryansky, A. Ya. Tsyganenko and N. V. Pavlenko, Chemistry ofBiogenic Elements, Vysha Shkola, Kiev, 1990.
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Atmosphere of Inhabited Areas, approved by Chief State Medical Officerof the USSR, 27 August 1984, No. 3086-84.
104. A. Reiner, Neue Hutte, 1985, 30, 337.105. Method for mercury removal from gases, USSR Pat., 1 161 157.106. C. O. Gale and E. L. Hill, Apparatus and method for continuous retorting
of mercury from ores and others mercury contaminated materials, USPat., 6 268 590, 2001.
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50B, 6944.113. US Environmental Protection Agency,Method 1631, Revision E: Mercury
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114. US Environmental Protection Agency,Mercury Study Report to Progress,Volume III: Fate and Transport of Mercury in the Environment, December1997, http://www.epa.gov/ttn/oarpg/t3/reports/volume3.pdf.
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CHAPTER 13
Demercurization Processes inDifferent Sectors of Industry
LEONID F. KOZIN,a STEVE C. HANSENb ANDNIKOLAI F. ZAKHARCHENKOa
aV. I. Vernadsky Institute of General and Inorganic Chemistry, NationalAcademy of Sciences of Ukraine, Kiev, Ukraine; b Consultant
13.1 Introduction
In this chapter, special attention is given to methods of demercurization ofchlor-alkali plants, recycling of spent fluorescent lamps, decontamination ofindustrial wastewater and demercurization of contaminated spaces to reduceairborne mercury levels dramatically to acceptable levels. Mercury formsmono- and divalent compounds. The monovalent compounds are poorlysoluble in water, whereas divalent mercury compounds are characterized byhigh solubility (with the exception of mercury sulfide). Mercury compounds aremostly unstable and decompose under the influence of heat and some evenunder the action of light. Mercury forms numerous complexes with organicmolecules, and also with inorganic ions. The properties of mercury compounds– the ability to dissolve in water and other environments, resistance to thermalstresses – are important when determining the method of chemicaldemercurization.1
13.2 Demercurization of a Chlor-Alkali Plant
An example of demercurization of a chlor-alkali plant is the work doneat the Pavlograd Khimprom (Chemical Industry) in the city of Pavlograd in
Mercury Handbook: Chemistry, Applications and Environmental Impact
By Leonid F Kozin and Steve Hansen
r L F Kozin and S C Hansen 2013
Published by the Royal Society of Chemistry, www.rsc.org
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the Republic of Kazakhstan.2 During the period of operation from 1975to 1993, the mercury-cell chlor-alkali plants lost over 1000 t of mercury.The first phase of demercurization included dismantling and disposal ofthe processing equipment, manual collection of metallic mercury anddisassembly of the mercury-contaminated production complex. Mercuryinfiltrated the land on which the complex stood. Therefore, the surfacelayer of heavily polluted soil down to a thickness of 1 m was removed torepositories and thereby isolated from the atmosphere and groundwater.Mercury extraction installations were constructed for lightly contaminatedmaterials.
Akhmetov and Bednenko2 noted that in the spring of 1999, when the elec-trolysis shop was opened, intensive evaporation of metallic mercury spillsbegan. The plant territory was declared an emergency zone and remained assuch for 2 months until complete tearing down of the electrolysis room and thecompletion of manual collection of 17 t of bulk mercury that had been spilled.This is less than 1.7% of the overall spilled mercury, which amounted tomore than 1000 t of metallic mercury, with a present-day cost of millions ofdollars.
The same fate befell the Kiev chlor-alkali production facility in theDarnitskiy district of Kiev, Ukraine. In the opinion of the authors, thesefigures testify to the poor level of planning at the mercury-cell chlor-alkaliplant. In the electrolysis shops of these chlor-alkali plants, it was essential toprovide sloping floors and ceilings (all-welded metal) impervious to mercuryand with airtight traps, to develop non-wettable concrete impervious tomercury vapor and automated removal of mercury from the traps, etc.Enormous losses of metallic mercury in the chlor-alkali industry have broughtabout catastrophic effects on the ecology of dozens of square kilometers, fromthe surface of the land down to subsurface waters. This led to the dismantlingof factories and the creation of ‘eternal’ landfills in which the mercury contentis higher than that of mercury-bearing ores and which will forever ‘breathe’poisonous mercury vapors, bringing death to warm-blooded animals andhumans. It should be noted that the maximum allowable concentration(MAC) of mercury in air is 0.0003mgm–3 and the maximum allowableconcentration in the soil is 2.1 mg kg–1. Hence it is easy to calculate what anenormous area of the Earth’s surface and what amount of land (soil) andgroundwater have been turned into dead zones by 1000 t of ‘lost’ mercury atthe Pavlograd Khimprom. Moreover, the mercury-cell chlor-alkali industry islarge scale and ranks third in world consumption of mercury, which, evenwith a considerable reduction of production in 2005, for example, consumed500 t of mercury.3 The composition of wastewater from chlorine and causticsoda production is as follows (mg dm–3):
Hg20 45–60Hg0 15Na2CO3 0.4–0.8NaOH 4.5–5.8NaCl 145–10 000
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Fe20 4.9–5.6NaClO 20.0Available chlorine 10.0Suspended particles B1000
with a p of 11–12.4–6
An example of ‘careful’ handling of mercury and amalgam is the amalgammetallurgy used to obtain high-purity metals.7–11 In this case, sealed elec-trolyzers are placed on special catch trays provided for the collection ofamalgams in case of theoretically possible accidents at the electrolyzers. Theequipment is fabricated from Plexiglas sheet (thickness 20–40mm) for thewalls and block Plexiglas (thickness 100 mm) for the floors of electrolyzers.The operating lifetime of electrolyzers prior to the appearance of thespiderweb cracking arrangement of Plexiglas was 10 years at an operatingtemperature of 40–451C. However, during operations at the high-purity metalshop at the Chimkent Lead Plant (CLP), not a single accident has occurredsince 1962 in the production of high-purity metals (cadmium Kd-0000, indiumIn-0000, thallium Tl-0000) in electrolyzers, each containing 500–600 kg ofmercury, and also high-purity lead Pb-000 and Pb-0000 and bismuth Bi-000and Bi-0000.8–11 Plexiglas electrolyzers were used to obtain high-puritycadmium, indium and thallium and contained 500–600 kg of mercury each,while electrolyzers used for high-purity lead and bismuth each contained1300–1400 kg of metallic mercury in the form of amalgams. Furthermore, thecontent of mercury vapor in the working premises of the shops was two ordersof magnitude below the MAC. Therefore, the pure metals department at theCLP, which was distinguished by an unusually high purity, was considered byfactory management to be a sanatorium and therefore highly skilledcraftsmen and skilled workers who had received overexposure in other leadproduction shops were sent there to work in the pure metals department. Thisexample shows that large amounts of mercury can be processed withoutharming the environment.8–11
13.3 Recycling of Fluorescent Lamps
The second highest mercury-consuming industry is the manufacture of fluor-escent lamps. In the production of fluorescent lamps, each of which contains1–10mg of mercury, up to 120–150 tons of mercury were consumed in 2005. Ifwe consider that the operating lifetime of fluorescent lamps will not exceed 1year owing to cracking and low mechanical durability, then it becomes clearthat the production of fluorescent lamps is a source of environmental hazards.
13.3.1 Thermal Demercurization of Fluorescent Lamps
For this reason, the world is developing technologies for demercurizingdiscarded fluorescent lamps.12–20 For example, let us examine the technology ofthe thermal demercurization of fluorescent lamps.19 A demercurizationflowsheet is shown in ref. 17.
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Fluorescent lamps and the waste material from their production arecomminuted and are transported for demercurization in a reactor containing a0.96–3.43 gL–1 solution of elemental sulfur in propylene carbonate. Thissolution circulates in a closed loop at 50–100 1C. Propylene carbonate, a sulfursolvent, has the following physiochemical properties: molecular weight,102.09 gmol–1; melting temperature, 70 1C; boiling point, 240 1C; density,1.204 g cm–3; and viscosity at 25 1C, 3mm2 s–1.
The reactor used for implementing this method contains a load and crushunit, coupled with a demercurization unit and centrifuge. The centrifugeseparates the mercuric sulfide formed at high speed by the reaction
SþHg� ! HgS # ð13:1Þ
with precipitation of HgS into a crystal sediment.The solution proceeds from the centrifuge to sump. The working solution
preparation unit is connected to a pump. The unit is equipped with a filter todispose of released gases that contain mercury vapor.
A fluorescent lamp is placed in the load and crush unit, which is linked byan emission-preventing airlock with the demercurization unit where it iscrushed, and glass fragments flow into the demercurization unit. Here, theprocess of binding mercury into sulfide occurs via mixing in the workingsolution. Mercuric sulfide, phosphor and fine glass dust are washed off withexcess solution from the glass fragments and, together with spent solution,proceed to the sump. Glass fragments proceed to the centrifuge for finaldisposal of spent solution C, which also enters the sump and dried glassfragments, III, are unloaded for further processing. Clarified solutionproceeds to the working solution preparation unit, where it is thermostatedand saturated with sulfur. Then working solution A is fed by a circulationpump into the demercurizer and is discharged into a gas filter which connectsthe load and crush unit with the atmosphere and prevents the ingress ofmercury vapor into the crush unit. For the complete removal of mercuryvapor from the load, discharged gases are circulated through them. Excess gasis dispelled into the atmosphere. Solution B and the mercury sulfide presenttherein, having passed through the filter, proceed to unit 2. Precipitate fromthe sump is unloaded as needed.
The loss of working solution during HgS precipitation carried awayby glass fragments, phosphor and glass dust after centrifuging and rinsingmade up 0.026–0.037% of the weight of the demercurized scrap. Overall, ourresults imply that at 50–100 1C the proposed technology17 allows completebinding of free-form and amalgamated metallic mercury7 into mercuricsulfide.
From the above, it follows that in order to improve environmental safety,pollution from mercury and its compounds should not be allowed in theenvironment and fluorescent lamps should be handled with great care. Spentfluorescent lamps are regarded as toxic mercury-containing wastes of thefirst hazard class and are buried at hazardous waste sites. According to the
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All-Union Institute of Secondary Resources (VIVR), the disposal cost oflamps, for example, at the Krasny Bor site, in the Leningrad region, cost 513rubles (BUS$19) per 1000 fluorescent lamps in 1980 and since 1995 the pricehas risen to US$500 per 1000 lamps. Moreover, disposal of fluorescent lamps isaccompanied by continuous expropriation of land and excludes the recla-mation of secondary resources such as mercury, metal (aluminum, tin,tungsten, nickel), phosphors and glass fragments. Complete recycling of spentfluorescent lamps leads to the prevention of environmental pollution bymercury and its compounds and also results in macroeconomic turnover of theabove-mentioned secondary resources. The average annual number of spentfluorescent lamps (in millions) is B160 in Russia, B40 in Ukraine, B12 inKazakhstan and B9 in Belarus. The entire world now produces about 1.5billion fluorescent lamps per year and uses about 4000 t of mercury in theirproduction.
Attempts are being made to develop improved technologies for processingfluorescent lamps. The VIVR developed a pyrometallurgical method forprocessing the lamps. At the core of the technology are the processes ofcrushing the fluorescent tubes and thermal distillation of mercury. However,the interaction of mercury with metals and organics at high temperatures(400–600 1C) forms a mercury-containing resinous mass. Moreover, mercury is‘spread’ by the given unit. There have been a multitude of other attempts todevelop technologies for the recycling of spent and defective fluorescenttubes21–23 which have failed in their practical implementation. These processeshave proven inferior to the technologies developed in more recent years.16–20
13.3.2 Vibration–Pneumatic Demercurization Method
The Ecotrom-2 unit16 is distinguished by high performance and low specificenergy output ratio (per recycled standard low-pressure discharge lamp).Therefore, with overall electricity consumption practically equal to knownthermal mercury lamp recycling units, Ecotrom-2 is much more productive (theproductivity of a thermal unit is typically 180–200 tubes per hour, whereas theproductivity of Ecotrom-2 is 1200 tubes per hour). The unit cost of water andcompressed air needed to operate the Ecotrom-2 unit is also almost two times less.
The vibration–pneumatic demercurization unit Ecotrom-2 consists of twomain units:
1. A lamp disintegration device, including a loading node, apneumatic–vibrational separator with a crusher and a centrifugalseparator (with an emission purification efficiency of 95–97%).
2. A multistage system for purifying waste gases: a hose filter (with apurifying efficiency of 99.96%), adsorbers (activated carbon) and a gasblower with a compressor.
The compressor creates a vacuum within the demercurization unit (from 5–8kPa in the lamp loading zone to 19–23 kPa prior to gas blowing), which
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eliminates the possibility of dust and gas emissions in the production room,permits complete capture of fluorescent lamp dust and reduces the mercurycontent in waste gases to less than 0.0001mgm–3.
Fluorescent lamps are processed by the Ecotrom-2 demercurization unit asfollows (see ref. 16). Lamps that arrive at the plant in special containers aredirected to the loading node. They are then fed through an accelerating tube viathe high-vacuum force existing within the unit that sends them to a separator inwhich they are crushed into glass with a fineness of less than 8 mm. The lampbases are separated from the glass on a vibrating screen and proceed to a specialcollector (process container) which, when filled, is directed to the demer-curization/roasting electric furnace where the bases are demercurized. Effluentgases from the furnace are diverted into the existing purification system.Phosphors are separated from the glass via blowing off in a vibrationalcountercurrent air/glass system. Phosphors that have been cleared of glassfragments then proceed to the storage hopper. The bulk of the phosphor(95–97%) is collected in a centrifugal separator and is accumulated inconveniently transportable metallic barrels with a polyethylene liner bag and asealed lid. The phosphor that is not collected in the centrifugal separatorprecipitates into the receiver of the hose filter and is then packed into the above-mentioned containers. Mercury-containing phosphors and sorbent are sent forfurther processing (to obtain metallic mercury).
13.3.3 Hydrometallurgical Treatment for Fluorescent
Lamp Recycling
We have also developed a highly effective hydrometallurgical technology forprocessing spent fluorescent lamps, allowing the recovery of metallic mercury,tin–lead–aluminum scrap and concentrated components of phosphor. Theprocess diagram for fluorescent lamp conversion is presented in ref. 24.
As is shown, the process for converting spent fluorescent lamps includesmechanical crushing of the fluorescent lamps under a layer of solventdissolution of mercury via redox reaction with an Fe(III) complex, elec-troreduction of mercury in an electrolyzer with a fluidized cathode, acidifi-cation of mercury, electrorefining of mercury to high purity and sorting offragments including separation and flushing of glass fragments and oxides,sulfides and basic salts and metallic scrap. Process water is sent for ion-exchange treatment to remove trace mercury. Secondary removal of mercuryfrom the water is then directed to the service tank. As mercury is accumulatedin ion-exchange columns, ions are regenerated via standard techniques. Theproposed technology is highly productive and permits the conversion ofproducts that comply with the appropriate MACs for mercury.4,7,25,26
Moreover, mercury recycling is close to 100%.It follows from the above that in many industries and in nature, mercury is
dispersed and, as was noted in Chapter 12, ‘spreads’ throughout the planet. Inmacroquantities, mercury has a toxic effect on the human body.4,7,25–34
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Consequently, when working with mercury it is necessary to performthoroughly precautionary measures that prevent even small traces of mercuryfrom entering not only the human body, but also the environment. Techniquesfor working with mercury that ensure the safety of the unit’s service personnelhave been described in many studies and manuals.7,25,35–39
13.4 Removal of Mercury from Industrial Wastewater
Various groups30,35,40–42 have examined methods for the complete removal ofmercury from industrial wastewater and utility emissions with a purificationrate of 97–99.5% and thereby ensured water with mercury contents below theMAC of 0.001mgL–1 for drinking water,4 no more than 0.005mgL–1 forutility facilities4 and 0.01mgm–3 for purified air masses of industrialplants.26,28–31 It is common for industrial wastewater to contain mercuryconcentrations that exceed the MAC by tens or hundreds of times. Thisincludes waste produced by a wide range of industries, including phar-maceuticals, textiles, paper, paints and varnishes and instrument making. Italso includes wastewater from the production of chlorine, caustic soda,tanning products and explosive materials, and further from the metallurgicaland electrochemical industries.
Combined methods are used to remove mercury from industrial water. Theprocess diagram for treating wastewater from chlorine and alkali production isdisplayed in ref. 24. The process diagram combines the stages for adjusting thepH to 2.5–4 (1) using HCl (2), oxidation of metallic mercury by elementalchlorine and adsorption in a solution, via activated carbon (3), or modified bycellulose complexing agents, to a mercury concentration of 0.1 mg dm–3,filtration of solid suspended particles (4), dechlorination on activated carbon(5) and ion-exchange treatment (6 and 7).
Ion-exchange treatment of industrial waters employs mercury sorption viathe ion exchange resin Mtilon T,5,44,45 the synthetic cation KU-2-8 in H-formor klinoptilolite, aminated muriatic methylamine,6 anions of type AB-17,VP-1AP, RMT, RNH and sulfur-containing cations of type KC, F-0¼ 243 andRG¼KSHL with sulfhydryl functional groups.24,43 Ion-exchange methodsallow the polishing and treatment of industrial wastewater to mercury concen-trations of 0.01–0.001mgdm–3,5,6,24,44,45 though according to other data 43 thisfigure may be as high as 0.005mgdm–3.
Mercury in ion-exchange resins is in the form of complex compounds and,for example, reaches 120 gL–1 in the ion-exchange resin VP-1AP. In thismaterial, mercury is bound in stable R–NCH3HgCl3
– complexes on its surfaceand in pores and is extracted only by alkaline solutions of sodium sulfidecontaining 5–12% Na2Sþ 4% NaOH.43 Mercury is desorbed from the anion inthe form of mercury disulfide, Na2HgS2. It is forced out of the mercury disulfidesolution via electrolytic precipitation by powdered aluminum or granulatedzinc or it is recovered by SnCl2, hydrazine hydrate, formaldehyde and FeSO4 ata concentration of 8–25 g -dm–3 of mercury disulfide solution. When FeSO4 is
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applied as a regenerant solution, mercury is converted to mercury sulfideaccording to the reaction
Na2HgS2 þ FeSO4 ! Na2SO4 þHgSþ FeS ð13:2Þ
and is removed via filtration in a mixture with iron sulfide. In all remainingcases cited above, mercury is separated out in the form of fine metallic mercury,which is difficult to remove from solution. The process diagram for regen-erating VP-1AP is presented in ref. 43. The diagram includes the regenerationstage of the VP-1AP anions via a sulfide–alkaline solution, flushing the sulfideions from the anions with a 5% solution of NaOH and water (up to a pH of 7).Subsequently, the anions are sent to a device for presorption treatment,precipitation of mercury from the regenerant solution in the form of mercurysulfide via iron(II) sulfate treatment and separation of mercury-containingsludge. The sludge is then sent for conversion in furnaces for thermal regen-eration of mercury sludge.43 The mercury recycling rate of the specified processis 98%. The wastewater treatment yield via ion exchange with VP-1AP ion is0.005mgHgL–1 of treated wastewater.43 This concentration complies with themercury MAC established for utility water facilities but does not comply withthe international standard MAC of 0.0001mgL–1.4,25,26 Consequently, tech-niques are being developed for advanced removal of mercury from wastewater.
13.5 Demercurization of Workplaces and Plants
As noted above, mercury is widely used in science, engineering and industry.Mercury contamination of production facilities occurs during emergencies,accidental spills and improper handling of mercury. Therefore, in this section wehave consolidated the results obtained from the development of methods fordemercurizing facilities, the most important of which is the demercurization ofworkspaces without contaminating them with common impurities. Normally,demercurization is carried out using a number of solutions possessingoxidizing properties in relation to mercury.25,35–39 These include a 20% solutionof iron(III) chloride, a 1–5% solution of potassium permanganate, a 4–5%solution of mono- or dichloramine in carbon tetrachloride, then a 4–5% solutionof sodium polysulfide and a 2.5% solution prepared from a mixture containing15–20% of ethylenediaminetetraacetic acid (EDTA) and 85–80% thiosulfate.
The demercurization methodology has been described.35–38 Prior to demer-curization, metal equipment is thoroughly cleaned and removed from the roomowing to the high corrosiveness of iron(III) chloride. Then the visible mercuryis removed from contaminated surfaces by mechanical means (by use ofvacuum or in traps). Next, the contaminated surface is treated with theappropriate solution, for example, with an iron(III) chloride solution based ona ratio of 1 bucket of solution to an area of 25 m2. According to Pugachevich,36
the surface covered with solution is wiped with a brush several times and is leftfor 1–2 days until completely dry. Then the demercurized surface is thoroughlycleansed with clean water. To remove drops of mercury, Jaeger39 recommended
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sprinkling the floor with zinc dust, copper powder or activated carbon treatedwith iodine. Activated carbon that has not been treated with iodine has lowactivity in relation to mercury. The products of the reaction between mercuryand the listed reagents are removed.
These methods are not ‘clean’ in relation to mercury and they create impuritysources. Moreover, these proposed methods do not allow demercurization of thewalls and ceilings of workspaces. When working with mercury, vapors infiltrateand are absorbed by the surface layers of paint, walls and ceilings withconcentrations lower than the MAC. To demercurize workspaces with anairborne mercury vapor content exceeding 80 MAC norms due to accumulatedand ‘spread’ mercury, we used the following technique.We removed the furnitureand equipment from the room, thoroughly sealed the windows and ventilationchannels and prepared materials to seal the doors. We humidified the room usingheating devices and boiling water and thereby humidified the walls. Then weplaced 50g of potassium permanganate in each of 2–3 flasks with volumes ofB2L and filled them with concentrated hydrochloric acid. A chlorine-releasingreaction occurred. The doors were then thoroughly sealed. The released chlorinereached the walls and infiltrated the porous surface layers of the walls and ceiling,where it interacted with the absorbed mercury, and formed calomel andmercury(II) chloride according to the following reactions:
Cl2 þ 2Hg0 ! Hg2Cl2 ð13:4Þ
Cl2 þHg0 ! HgCl2 ð13:5Þ
These reactions proceed at an enormously high rate. The standard electricpotential of the half-reaction Cl2þ 2e Ð 2Cl– is E�Cl2 =Cl� ¼þ 1.3595V.46
Moreover, in the presence of moisture (moist walls, ceiling, floor), chlorineundergoes a disproportionation reaction (Kuznetsov reaction):
Cl2 þH2OÐHClO þHCl ð13:6Þ
with the formation of a strong oxidant, hypochloric acid. The standardpotentials of the half-reactions
HClO þHþ þ eÐ1=2Cl2 þH2O ð13:7Þ
HClOþHþ þ 2eÐCl� þH2O ð13:8Þ
equal to E�HClO = 1=2 Cl2
¼þ 1.63 V and E�HClO =Cl� ¼þ 1.49 V, respectively,46
demonstrate the higher oxidizing power of hypochloric acid in comparisonwith chlorine.
The equilibrium constants of the reactions between HClO and mercury:
Hg0 þHClO þHCl! HgCl2 þH2O ð13:9Þ
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and
Hg0 þHClOþHCl! Hg2Cl2 þH2O ð13:10Þ
are 4.82 �10–37 and 1.06 �10–43, respectively, demonstrating the equilibriumshift of these reactions towards the formation of mercury(II) chloride andcalomel, which have practically zero volatility.
After applying such a method to treat a workspace with a mercury MACequal to 80 norms and after the space had been hermetically sealed for 3 days,the mercury content in the air after ventilation was reduced to 0.05 MAC. Afterthe room had been whitewashed with white titanium paint and cleaned, themercury content in the air was 0.01 MAC (1.0 ngm–3). Consequently, themercury vapor content in the air of the room was reduced 8000-fold afterdemercurization. The thermal method of demercurization, which combinesheating of the surface to 200–250 1C with sorbed mercury and vacuum ventingof mercury vapor, gives only a 40–50-fold reduction in mercury content inair.36,47
The positive side of this proposed method of workspace demercurization isthe conversion of metallic mercury into an inactive state and the creation, undera layer of fresh white titanium paint, of an oxidizing environment consisting ofadsorbed active oxygen (HClO) and traces of chlorine that continue to spreadinto the plaster and pores in the walls, thereby neutralizing the metallic mercurythat had accumulated over the years.
Methods of personal protection and personal preventive measures whenworking with mercury have been described in detail.25,35,38 Work must beperformed in starched protective clothing and leather or rubber footwearprotected by poly(vinyl chloride) covers. After work, protective work clothingis left in the workclothes room.
After working with mercury, one must thoroughly wash the face and handswith warm water and soap and take a shower.36 Also when working withmercury, special attention must be given to the condition of the mouth cavity.Teeth should be brushed twice per day (morning and night) and affected teethshould be treated in a timely manner.36 After work, one must rinse the mouthcavity with a 1% solution of Berthollet’s salt or a 5% solution of potassiumpermanganate. Food rich in vitamins and pectin must be consumed. In case ofworsening health, irritability, insomnia, bleeding gums, etc., a doctor must beconsulted. Special attention should be paid to a healthy lifestyle, such as a daily30–50 min morning exercise routine ending with hydrotherapeutic exercises,regular calisthenics, sports or mountain walking. Such activities increase thebody’s resistance and strengthen the nervous system.
References
1. A. G. Morachevskii, I. A. Shesterkin, V. B. Busse-Machukas, et al., Natrii.Svoistva, proizvodstvo, primenenie (Sodium. Properties, Production, Appli-cation), ed. A. G. Morachevskii, St. Petersburg, Khimiya, 1992.
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2. A. D. Akhmetov and V. A. Bednenko, Mercury pollution of theenvironment, emissions into the atmosphere, restoration of territories,impact on health, in Proceedings of the International Seminar, 28 May–1 June 2007, Astana, 2007, 18–19.
3. United Nations Environment Programme, Report on Current Supply andDemand for Mercury, Including Projections Considering the Phase-out ofPrimary Mercury Mining, UNEP (DTIE)/Hg/OEWG 2/6, UNEP, Nairobi,2008.
4. Ya. M. Grushko, Harmful Inorganic Compounds in Industrial Effluents,Khimiya, Leningrad, 1979.
5. V. F. Fedonina, M. O. Lishevskaya and N. S. Torocheshnikov, et al.,Khim. Prom., 1972, 1, 72–73.
6. S. M. Rustamov, I. I. Zeynalova, F. T. Makhmudov and Z. Z. Bashirova,Khim. Tekhnol. Vody (translated in J. Water Chem. Technol.), 1993, 15,378–382.
7. L. F. Kozin, Physicochemistry and Metallurgy of High-Purity Mercury andIts Alloys, Naukova Dumka, Kiev, 1992.
8. L. F. Kozin, A. G. Morachevskiy and I. A. Sheka, Ukr. Khim. Zh., 1989,55, 495–509.
9. L. F. Kozin and A. G. Morachevskiy, Physicochemistry and Metallurgy ofHigh-Purity Lead, Metallurgiya, Moscow, 1991.
10. L. F. Kozin and S. V. Volkov, Chemistry and Technology of High-PurityMetals and Metalloids, Volume 1. Chemical and Electrochemical Methodsfor Ultra-purification, Naukova Dumka, Kiev, 2002.
11. L. F. Kozin, Amalgam Metallurgy, Tekhnika, Kiev, 1970.12. UNEP, Assessment of Mercury Releases from the Russian Federation,
Arctic Council’s Action Plan to Prevent Pollution of the Arctic), DanishEnvironmental Protection Agency.
13. W. E. Walles and L. C. Mulford, US Pat., 5 478 540, 1995.14. A. Muratov, Nedelya, 1986, (18), April 28.15. Russian Ministry of Natural Resources, Certificate of Environmental
Compliance with Requirements of GOST R ISO 14001-98 Russian Ministryof Natural Resources No. 00000309 as of 02/28/2003, 2003.
16. N. A. Stolyarova, N. A. Chekhlan and E. A. Egorova, Utilization of fluor-escent lamps on the demercurization equipment {Ecotrom-2c http://ea.donntu.edu.ua:8080/jspui/bitstream/123456789/15694/1/Stolyarova%20N.%20A.%20.pdf. Accessed 13 July 2013.
17. A. P. Alekseev, N. G. Dmitrieva, A. M. Zorkal’tsev, V. V. Leonenko VV,and G. A. Safonov, Method for processing of electroluminescent lightsources and a device for its implementation, USSR Pat., 2 044 087.
18. O. V. Grigor’vich and S. V. Sergeevich, Demercurator, USSR Pat.,2 295 583.
19. V. N. Kovalev, A. N. Gorbenko, V. N. Timofeev and V. V. Ten, Methodfor thermal demercurization of mercury-containing materials and devicefor its implementation, USSR Pat., 2 171 304.
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20. Y. G. Dyachenko, A. A. Zakharov, A. G. Ljashenko, E. M. Ain, A. V.Agueyev and A. G. Gorobec, A device for fractionation in a unit formercury-containing fluorescent lamps recycling, USSR Pat., 2 191 638.
21. V. Grigorivich, V. S. Sergeevich and O. Vladimirovich, Method fordisposal of mercury-containing wastes, USSR Pat., 2 327 536.
22. C. R. Palmer and R. G. Sandberg, in Precious Metals, Mining, Extractionand Process, Proceedings of International Symposium, AIME AnnualMeeting, Los Angeles, CA., 27–29 February 1984, AIME, Warrendale, PA,1984, pp. 227–239.
23. Fr. Pat. Appl., 2 615 756.24. L. E. Postolov, T. E., Mitchenko and V. G. Ovchinnikov, Khim. Tekhnol.,
1992, (2) (182), 15.25. H. G. Seiler and H. Sigel (eds), Handbook on Toxicity of Inorganic
Compounds, Marcel Dekker, New York, 1988, pp. 419–436.26. N. V. Lazarev and I. D. Gadaskina (eds), Harmful Substances in Industry,
Inorganic and Organoelement Compounds, Khimiya, Leningrad, 1977.27. J. O’M. Bockris (ed.), Environmental Chemistry, Khimiya, Moscow, 1982.28. International Atomic Energy Agency, Mercury Contamination in Man and
His Environment, Tech. Rep. Ser., No. 137, IAEA, Vienna, 1972, p. 177.29. L. Friberg and J. Vostal, Mercury in the Environment, CRC Press,
Cleveland, OH, 1982.30. I. M. Trachtenberg and M. N. Korshun, Mercury and Its Compounds in the
Environment, Vysha Shkola, Kiev, 1990.31. Ya. M. Grushko, Harmful Inorganic Compounds in Industrial Emissions
into the Atmosphere, Khimiya, Leningrad, 1987.32. V. G. Huhryansky, A. Ya. Tsyganenko and N. V. Pavlenko, Chemistry of
Biogenic Elements, Vysha Shkola, Kiev, 1990.33. The Maximum Permissible Concentration (MPC) of Pollutants in the
Atmosphere of Inhabited Areas, Approved by Chief State Medical Officer ofthe USSR on 27 August 1984, No. 3086-84.
34. V. N. Kurnosov, Maximum Allowable Concentrations of AtmosphericPollutants, Medgiz, Moscow, 1961, pp. 54–71.
35. Interindustrial Safety Rules in Production and Use of Mercury, POTRM-009-99, DEAN Publishing House, St. Petersburg, 2001, p. 64.
36. P. P. Pugachevich, Working with Mercury Under Laboratory and IndustrialConditions, Khimiya, Moscow, 1972.
37. S. M. Mel’nikov, Metallurgy of Mercury, Metallurgiya, Moscow, 1971.38. S. M. Mel’nikov, Safety in Metallurgy of Mercury, Metallurgiya, Moscow,
1974.39. H. Jaeger (ed.), Electrometallurgy of Aqueous Solutions, Industrial Elec-
trochemistry Reference Book, translation from German, Metallurgiya,Moscow, 1966.
40. T. O. Mamutovich, B. I. Ibrahimovic, A. A. Abildaevich and S. K.Sydykovich, Method for recycling of mercury-containing polymetallic rawmaterials, USSR Pat., 1 620 499.
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41. C. Nunez and F. Espiell, Met. Trans., 1986, B17, 443–448.42. C. Nunez and F. Espiell, Met. Trans., 1985, B15, 229–233.43. L. E. Postolov, T. E. Mitchenko, V. A. Skripnik and A. M. Roitenberg,
Khim. Tekhnol., 1984, 4, 35.44. Z. A. Rogovin, M. O. Lishevskaya, V. V. Voronenko and B. F. Fedyunina,
Khim.Prom., 1966, No. 7, 512.45. Method for wastewater treatment from metals, USSR Pat., 230 738.46. V. Latimer, The Oxidation States of the Elements and Their Potentials in
Aqueous Solutions, Izdatel’stvo Inostrannaya Literatura, Moscow, 1954,p. 400.
47. H. B. Masters, Min. Annu. Rev., 1988, June, 91–95.
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CHAPTER 14
Safety and Health Practices forWorking with Metallic Mercuryy
WOODHALL STOPFORD
Duke University Medical Center, Durham, NC 27710, USA
14.1 Toxicity of Metallic Mercury
Acute mercury toxicity can occur when mercury is inhaled in milligramquantities. Such exposures are invariably associated with work in a confined,mercury-contaminated space with little ventilation or by heating of mercurysuch as in home amalgamation efforts, welding of contaminated surfaces orspills of hot mercury. After a delay of a few hours, a metal fume fever canresult, with symptoms of nausea, abdominal cramps, diarrhea, muscle aches,fever and an elevated white blood cell count.
With higher exposures, one can also see symptoms of pulmonary irritationwith chest tightness, a cough and shortness of breath. X-rays of the chest in thisdisorder disclose an interstitial pneumonitis and pulmonary function tests showrestrictive changes and also a diffusion defect for oxygen. Survivors can developchronic shortness of breath and interstitial fibrosis of the lungs. Possibly morecommon than pulmonary toxicity is inflammation of the mouth. Shortly afteran acute exposure, the mouth and gums can become red and sore. Within a fewdays, patients can experience a metallic taste together with further inflam-mation of the gums, loosening of the teeth, ulcers of the mouth and a blue lineat the gum margins. Occasionally, a tremor is noted and, less commonly,bloody diarrhea and transient liver and kidney abnormalities.
yProvided by Bethlehem Apparatus, Inc. Hellertown, PA.
Mercury Handbook: Chemistry, Applications and Environmental Impact
By Leonid F Kozin and Steve Hansen
r L F Kozin and S C Hansen 2013
Published by the Royal Society of Chemistry, www.rsc.org
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14.2 Toxicity from Chronic Exposure
In industry, the earliest finding that might be noted from chronic exposure tomoderate levels of metallic mercury is that of a tremor. It is initially seen as afine, postural tremor noted only when the arms are outstretched. With greaterexposures or exposures of longer duration, the tremor increases in amplitudeand becomes coarse. In addition, it appears to be aggravated by intentionalactivities such as writing or picking up a cup or coffee. As the severity of thetremor increases, it can be interrupted by clonic-like jerks of one or moreextremities. In the severest cases, these jerks progress to involve the entire body.
Sometimes, associated with a moderate tremor there is difficulty inperforming fine movements, incoordination, difficulty with gait and evenhoarseness associated with ataxia of the vocal cords.
If mercury exposure continues to the point of the development of asignificant tremor, a state of erethism can sometimes be found. Affectedworkers become easily upset and embarrassed, irritable and sometimes quar-relsome. They lose self-confidence and often have a feeling as if they are beingwatched. If they think they are being watched, their tremor activity mightincrease in severity. They often have difficulties with sleeping or havenightmares. Some tend to be drowsy and fall asleep on the job. Often there isdepression and memory loss associated with mercury exposure. Rarely thereare hallucinations, delusions or mania. All findings and complaints of anindividual who manifests eresthismic symptoms can be resolved over a periodof months without any further intervention if the individual is removed fromexposure to mercury.
With extreme exposures to metallic mercury, one can find concentricconstruction of the visual fields, poor night vision and red–green colorblindness, problems that can be resolved by treatment with chelating agents.A more common eye problem is the finding of mercurialentis, e.g., a brownishdiscoloration of the anterior capsule of the lens. Such a defect occurs only afterchronic exposure to mercury and can be present without any evidence ofmercurialism.
Individuals who have severe mercurialism can also have symptomatic defectsof other sensory organs. These include a high frequency hearing loss, symptomsof vertigo, ringing in the ears, loss of balance and a partial loss of smell sense.In workers with severe mercurialism secondary to inorganic mercury exposure,one can sometimes find disorders of the spinal cord and peripheral nerves,including a syndrome resembling amyotrophic lateral sclerosis (ALS), disordersof the sensory nerves and a Parkinsonism-like syndrome of stiffness and rigidityof the extremities.
A common manifestation of chronic exposure to excessive levels of mercuryvapor is gum disease. The gums initially become swollen and boggy and laterretract. In individuals who have pre-existing pyorrhea, evidence of infectioncan be aggravated. In severe cases, there can be loosening of the teeth with bonyreabsorption of the jaw. The gum disease can be brought under control withgood oral hygiene even if exposure to mercury continues. Individuals who have
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jaw involvement can improve if they are taken out of exposure and treated withbraces.
Once inorganic mercury enters the body, it is primarily stored in the proximaltubules of the kidney. It is not unexpected, therefore, that the earliest signs ofkidney damage would be manifested by a disorder of the proximal tubules.These tubules are involved with reabsorption of nutrients and substances thatare normally filtered into the urine, but are usually conserved by the body. Withproximal tubular disease secondary to mercury, one can find abnormalamounts of glucose, phosphate, amino acids and low molecular weight proteinsin the urine.
Unfortunately, studies of renal tubular disease are difficult and oftenproteinuria from a glomerular injury is the first manifestation of kidney toxicitysecondary to excessive absorption of mercury. On biopsy of an individual withsuch a problem, one finds evidence of a membranous glomerulonephritis inassociation with proximal tubular injury.
Inorganic mercury is unusual in that it is lost relatively rapidly from thebody. In a worker with early manifestations of mercury toxicity of any organ,improvement and complete resolution of the problem are almost invariablynoted when the worker is removed from exposure for a period of time.If excessive exposure continues in the face of obvious clinical problems or ifthere are recurrent exposures and toxicity, manifestations of mercurialism canbecome chronic. Manifestations can include tremors, paralysis, loss of memoryand chronic renal disease. Over the past 20 years, cases of chronic inorganicmercurialism have been reported only sporadically and have only been notedafter exposures that were severe, uncontrolled and prolonged.
14.3 Surveillance Programs for Industry
A pre-employment examination program is needed to identify and restrictcertain individuals from potential exposure to mercury. Exposure is contrain-dicated in those individuals who have problems that might be either aggravatedwith mercury exposure or confused with findings of mercurialism and thushinder the effectiveness of a medical monitoring program. Problems whichwould restrict employment include
� alcoholism� chronic kidney disease� known allergy to mercury.
If protein is found in a urine specimen, but there is evidence of chronickidney disease, the individual can be employed once the underlying problemhas been corrected. Individuals with evidence of gingivitis (gum inflammation)should be under the care of a dentist prior to employment. Tremor andpsychological problems should be documented.
There has always been difficulty in correlating measured exposure levels tomercury vapor with biological measurements of mercury absorption except
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when data are analyzed on a group basis. Most studies that correlate biologicallevels with air levels are based on area vapor measurements. However, whenthere is a potential exposure to metallic mercury, personal contamination canresult with the formation of a microenvironment of mercury vapor around theworker’s breathing zone that is several times higher than that of the generalwork environment. If work clothes are brought home, contamination of thehome can result in exposures that continue for a longer period than the workday, and also exposure to family members.
Environmental monitoring should include daily area mercury vapor levels atall work sites by direct measurement of mercury vapor concentration andperiodic time-weighted average breathing zone measurements. Measurementscan be made with a gold foil monitor or a portable personal sampling pumpconnected to Hopcalite tube.
Urine mercury levels are useful for estimating both exposures and bodyburden since most inorganic mercury that is absorbed is deposited in thekidneys prior to excretion. Urine mercury levels tend to vary from person toperson with similar exposures and also from time to time in the same indi-vidual. In order to make urine mercury determinations more reflective of anindividual’s exposure, efforts have been made to decrease the variability inmeasurements. By making urine mercury determinations on the same day eachweek and the same time of day, the variability seen in any one individual’s urinemercury determinations can be decreased. Corrections for urine concentrationby using either the excretion of creatinine or urine specific gravity can alsodecrease the variability between urine mercury determinations. Corrections forvariability in urine concentration can be avoided by using for analysis the firstvoided specimen on rising.
Determinations of mercury in whole blood are better indicators of currentexposure than urine mercury determinations. In humans, the initial half-life forloss of mercury from blood is also fairly short, B5 days. There is an excellentcorrelation between blood mercury levels and average area mercury vaporlevels or breathing zone mercury vapor levels.
Some individuals can excrete milligrams of mercury per liter of urine withoutany evidence of ill-effect, whereas others might excrete less than 300 mgL–1 andhave evidence of adverse effects from mercury exposure. Because of thisvariation in susceptibility, only a detailed medical monitoring program canidentify those individuals who are having adverse effects from mercuryexposure. Such an examination should include a complete history, emphasizingneurological and psychological complaints, and also complete physical exam-ination with emphasis on the oropharyngeal and neurological components ofthe examination. Certain physiological studies are indicated. Periodic tests ofstrength can be made with a simple grip gauge. The severity of a tremor can bedocumented. An important part of the medical examination is a closeassessment of kidney function. One simple way is to assess total proteinexcretion quantitatively. Urine glucose and albumin levels can easily bechecked with an indicator strip. Periodic blood tests to assess kidney functionshould be performed.
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14.4 Preventive Measures
Metallic mercury that is spilled on a floor surface is available not only forvaporization, but also for tracking into all parts of the facility with resultantexposure to workers who might normally not be exposed to mercury vapor. Toprevent this type of contamination, floors should be sealed with an epoxy sealerand washed periodically with trisodium phosphate solution to remove all smallparticles of mercury. More obvious spills of mercury should be vacuumed intoa water trap at the time of the occurrence of the spill. The vacuum should beappropriately exhausted or filtered to prevent further mercury exposure. Analternative method of picking up mercury spills is to use a copper pad filled withzinc filings to amalgamate the mercury.
In areas where the working surface cannot be sealed, either a solution ofcalcium polysulfide in a wetting agent or a 20% solution of ferric chloride canbe sprayed on to the surface. This treatment will adequately suppress mercuryvapor production until the surface is disturbed.
Smoking should not be allowed in mercury exposure areas. Furthermore,tobacco products should not be kept in shop areas. Cigarettes canreadily absorb mercury vapor and therefore should not be brought into an areawhere mercury is used. Furthermore, cigarettes can be readily contaminatedby being laid down on a work surface or by being smoked prior to washingone’s hands. The cigarette can then readily volatilize any mercurypresent, giving excessive exposure not only to the smoker, but also to anyonenearby.
In addition to creating an excessive microenvironmental level of mercuryvapor around a worker’s face, personal contamination can also lead toexcessive absorption through the skin. To help prevent skin contamination, notonly should adequate laboratory garments be worn, but also either glovesshould be worn or thiosulfate-containing barrier cream should be applied toprotect the hands. Hands should be washed before smoking or drinking. Withexposure to levels of mercury vapor less than 0.5mgm–3, a silver-impregnateddust mask can be worn. With higher exposures, a chemical cartridge respirator(e.g., Mersorb-MGA) should be used. Accumulation of mercury-containingdust on the outside of the mercury vapor absorptive masks can also lead to therapid breakthrough of these masks and excessive mercury exposure to workersabove and beyond what they would receive without wearing the mask.A frequently changed dust filter in front of the cartridge can prevent thisproblem. When working in an environment with a very high concentration ofmercury vapor, a full face mask should be worn to prevent excessive absorptionof mercury vapor through the cornea with resultant incapacities of the corneaand lens.
Underwear and socks can absorb mercury excreted in sweat and, in turn,make this mercury available for reabsorption through either the skin or therespiratory tract. Although relatively minor, reabsorption of mercury fromsweat can be prevented by changing underwear and showering at the end ofeach working day.
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One of the major ways of decreasing workers’ exposure to mercury is byadequate ventilation. In a stagnant environment, even at 0 1C, a dangerousexposure situation to mercury vapor can result. As the temperature increases,the vapor pressure of mercury increases rapidly such that at 30 1C there is anapproximately sixfold greater vapor level than at 0 1C under the sameconditions. Adequate general ventilation is mandatory. During the summermonths, increased ventilation by opening all doors and windows is helpful.Under some circumstances, it is easier to use air conditioning to keep thetemperature down and vapor levels under control without any drastic changesin ventilation. High-volume local exhaust ventilation of point sources ofmercury vapor, such as contaminated ovens, can greatly decrease the overallventilation requirements of a facility and also prevent excessive levels ofmercury vapor in local work areas. Makeup air requirements can be decreasedby filtering recirculated air through mercury-absorbing activated charcoalfilters.
In situations where engineering controls are inadequate to control a mercuryvapor exposure, administrative controls can be used to decrease workerexposure and, thus, worker ill health. Excessive biological levels of mercury arenot an indication of mercury poisoning. Although biological results can be usedas an indication of excessive absorption and, thus, the need for improved workpractices, personal hygiene, engineering controls, personal protectiveequipment and safety measures, they should only be used with caution as abasis for administrative actions. If a medical examination discloses evidenceboth of absorption of mercury and of abnormalities that might be related tothis absorption, administrative action should be taken. The employee should beput into a low-exposure area until the abnormality has cleared and evidence ofexcessive absorption has disappeared. If abnormalities persist, further medicalevaluation is needed to look for other etiologic reasons for the abnormalities.
Mercury can present an environmental hazard through inappropriatedischarges of process or wash water, venting of contaminated air or disposal ofmercury-contaminated solid wastes. Waste water contaminated with mercurycan be adequately decontaminated prior to discharge with activated charcoal.Other systems are available based on sulfite deposition of mercury or by reverseosmosis. Mercury-absorbing activated charcoal can also be used to treat ventedair contaminated with high levels of mercury vapor. Work room air should bevented away from intake vents. In order to avoid disposing of mercury-contaminated solid wastes, such wastes should be sent to a facility equipped torecover mercury.
Metallic mercury exposures, when excessive, can produce various neurologic,oropharyngeal and renal problems that may be resolved spontaneously onceexposure has stopped. Chronic problems can develop with unusual exposuresthat are prolonged beyond the first clinical manifestation of mercurialism. Inthis situation, a number of findings, including constriction of visual fields, aParkinsonism-like syndrome and evidence of combined motor neuron diseasecan develop. However, these findings can be reversed by the use of an appro-priate therapy.
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Often there can be personal contamination of a worker with exposurethrough the skin and airways that cannot be detected by routine airmeasurements. For this reason, a biological and medical monitoring program isrequired to detect early manifestations of mercurialism and intervene at thetime when only administrative controls are required to resolve the problems.There are large variations in a worker’s susceptibility such that biological levelsof mercury by themselves should not be used as a basis for moving a worker toa low-exposure situation. With adequate work practices, personal protection,housekeeping and engineering controls, chronic exposures can be kept to aminimum and most of the hazards to workers eliminated.
Further Reading
H. B. Elkins, L. D. Pagnotto and H. L. Smith, Am. Ind. Hyg. Assoc. J., 1974,35, 559.
L. J. Goldwater, The Harben Lectures, J. R. Inst. Public Health Hyg., 1964, 27,279.
J. K. Piotrowski, B. Trojanowska and E. M. Mogilnicka, Int. Arch. Occup.Environ. Health, 1975, 35, 245.
M. Randall and H. B. Humphrey, New Process for Controlling MercuryVapor, US Bureau of Mines Information Circular No. 7206, US Bureau ofMines, Washington, DC, 1942.
A. O. Rathje, Am. Ind. Hyg. Assoc. J., 1969, 29, 126.J. Shurgan and L. Harris, Am. Ind. Hyg. Assoc. J., 1977, 38, 146.W. Stopford, Industrial exposure to mercury, in The Biogeochemistry ofMercury in the Environment, ed. J. O. Nriagu, Elsevier/North-Holland,Amsterdam, 1979, pp. 368–397.
W. Stopford, S. D. Bundy, L. J. Goldwater and J. A. Bittikofer, Am. Ind. Hyg.Assoc. J., 1978, 39, 378.
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APPENDIX I
Phase Diagrams andIntermetallic Compoundsin Binary Amalgam Systems
AI.1 Binary Mercury Phase Diagrams
Most metals in contact with mercury a peritectic reaction or a series of peri-tectic reactions called a peritectic cascade. Few systems do not show anyperitectic reactions. With several exceptions, notably lithium, zinc, cadmium,indium and thallium, mercury forms intermetallic compounds with little or nosolid solubility.
Alkali, alkaline earth, lanthanide and actinide metals react strongly withmercury and form a large number of intermetallic compounds. The inter-metallic phases formed in these systems generally have very narrow ranges ofhomogeneity. Transition metals (Ti, Zr, Hf, Mn, Ni, Cu, Rh, Pd, Pt, Cd, Zn,Ag and Au) typically form peritectic cascades and intermetallic compounds.Metalloids such as aluminum, antimony and bismuth form degenerate eutecticsystems. Gallium forms a simple monotectic reaction with mercury. Lead andtin also show intermetallic solid solutions and peritectic reaction sequences.The halogen–mercury systems form a syntectic reaction (L1þL2-HgX) withX¼F, Cl, Br and I.
A complete set of binary mercury phase diagrams is available as follows:C. Guminski, Contributions of electrochemistry to the knowledge of
amalgams, Pol. J. Chem., 2004, 78, 1733–1751.
AI.2 Intermetallic Phases in Binary Amalgam Systems
Intermetallic phases with crystal structure and lattice parameters whereavailable are given in the following tables, with relevant literature citations.
Mercury Handbook: Chemistry, Applications and Environmental Impact
By Leonid F Kozin and Steve Hansen
r L F Kozin and S C Hansen 2013
Published by the Royal Society of Chemistry, www.rsc.org
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Ag–Hg
Phase Crystal structureLatticeparameters (nm)
Density(g cm–3) Prototype
z 43–46%Hg Hexagonal closepacked
a¼ 0.2964,c¼ 0.4831
Mg
g 56–57%Hg Cubic a¼ 1.0046 13.65calc, 13.48meas
P. Anderson and S. J. Jensen, Chemical composition and crystal structure of theg-phase in the silver–mercury system, Scand. J. Dent. Res., 1971, 79, 466–471.
M. R. Baren, The Ag–Hg (silver–mercury) system, J. Phase Equilib., 1996, 17,122–128.
C. Cipriani, G. P. Bernardini, M. Corazza, G. Mazzetti and V. Moggi, Eur. J.Mineral., 1993, 5, 903–914.
C. W. Fairhurst and J. B. Cohen, The crystal structures of two compoundsfound in dental amalgam: Ag2Hg3 and Ag3Sn, Acta Crystallogr. B, 1972, 28,371–377.
S. J. Jensen, Neutron diffraction study of the g-phase in the silver–mercurysystem, Scand. J. Dent. Res., 1972, 80, 162–165.
E. Seeliger and A. Mucke, Para-schachnerite, Agl.2Hg0.8, and schachnerite,Agl.lHg0.9, from Landsbergite near Obermoschel, Pfalz, N. Jahrb. Mineral.Abhandl., 1972, 117, 1–18.
S. Stenbeck, X-ray analysis of alloys of mercury with silver, gold and tin,Z. Anorg. Chem., 1933, 214, 16–18.
Am–Hg
J. Maly, The amalgamation behavior of heavy elements, J. Inorg. Nucl. Chem.,1969, 31, 1007–1017.
M. F. Tikhonov, V. Z. Neponmyashchii, S. V. Kalinina, A. D. Khokhlov, V. I.Bulkin and B. M. Filin, Preparation of the Am amalgam, Radiokhimiya,1986, 28, 804–809.
Au–Hg
PhaseCrystalstructure
Lattice parameters(nm)
Density(g cm–3) Prototype
a1 16–23% Hg Hexagonal a¼ 0.8736, c¼ 0.9577z (Au3Hg) 21–26% Hg Hexagonal a¼ 0.2914, c¼ 0.4803 MgAu2Hg Hexagonal a¼ 0.7019, c¼ 1.0184 16.67calc Au2HgAu6Hg5 Hexagonal a¼ 1.308, c¼ 1.720 N6Nb5Au5Hg8 Cubic a¼ 0.992 Cu5Zn8
A. F. Berndt and J. D. Cummins, The crystal structure of the Au2Hg phase,Acta Crystallogr. B, 1970, 26, 864–867.
T. Lindahl, The crystal structure of Au6Hg5, Acta Chem. Scand., 1970, 24,946–952.
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T. B. Massalski, The lattice spacings of close-packed hexagonal Au–In, Au–Cdand Au–Hg alloys, Acta Metall., 1957, 5, 541–547.
H. Okamoto and T. B. Massalski, Bull. Alloy Phase Diagrams, 1989, 10, 50–58.C. Rolfe and W. Hume-Rothery, The constitution of alloys of gold andmercury, J. Less-Common Met., 1967, 13, 1–10.
S. Stenbeck, X-ray analysis of alloys of mercury with silver, gold and tin,Z. Anorg. Chem., 1933, 214, 16–18.
Ba–Hg
Phase Structure Lattice parameters (nm)Density(g cm–3) Protoype
Ba7Hg31 Tetragonal a¼ 1.0778, c¼ 1.0189 Ba7Cd31BaHg Cubic a¼ 0.4133 CsClBaHg2 Orthorhombic a¼ 0.5144, b¼ 0.8072, c¼ 0.8717 CeCu2BaHg6BaHg11 Cubic a¼ 0.95871 BaHg11BaHg13 CubicBa2Hg Tetragonal a¼ 0.4200, c¼ 1.519 Ba2CdBa14Hg51 Hexagonal
E. Biehl and H.-J. Deiseroth, Preparation, structural relations and magnetismof amalgams MHg11 (M: K, Rb, Ba, Sr), Z. Anorg. Allg. Chem., 1999, 625,1073–1080.
G. Bruzzone and F. Merlo, The barium–mercury system, J. Less-CommonMet., 1975, 39, 271–276.
C. Guminski, The Ba–Hg (barium–mercury) system, J. Phase Equilib., 2000,21, 173–178.
F. Merlo, The crystal structure of Ca3Cd2, Ba2Cd and Ba2Hg, J. Less-CommonMet., 1976, 50, 275–278.
Br–Hg
Phase Crystal structure Lattice parameters (nm) Density (g cm–3) Prototype
a-Hg2Br2 Orthorhombicb-Hg2Br2 tI16 a¼ 0.4666, c¼ 1.1133 Hg2Cl2HgBr2 oC12 HgBr2
H. Braekken, The crystal structure of HgBr2, Z. Kristallogr., 1932, 81, 152–154.E. Dorm, Intermetallic distances in Hg(I) halides Hg2F2, Hg2Cl2, Hg2Br2,J. Chem. Soc., Chem. Commun., 1971, 466–467.
R. Dworsky and K. Komarek, The Hg–Br system, Monatsh. Chem., 1970, 101,976–983.
C. Guminski, The Br–Hg (bromine–mercury) system, J. Phase Equilib., 2000,21, 539–543.
250 Appendix I
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R. J. Havighurst, Parameters in crystal structure: mercurous halides, J. Am.Chem. Soc., 1926, 48, 2113–2125.
H. E. Swanson, N. T. Gilfrich and M. I. Cooke, Standard XRD PowderPatterns, Circular 539, Pt. 7, National Bureau of Standarrds, Gaithersburg,MD, 1957, pp. 33–35.
Ca–Hg
Phase Crystal structure Lattice parameters (nm) Density (g cm–3) Protoype
CaHg Cubic a¼ 0.3758 CsClCaHg2 Trigonal a¼ 0.4894, c¼ 0.3571 CeCd2CaHg3 Hexagonal a¼ 0.6635, c¼ 0.502 Ni3SnCaHg8–11 Cubic BaHg11Ca2Hg Orthorhombic a¼ 0.786, b¼ 0.489,
c¼ 0.987Co2Si(Ni2Si)
Ca3Hg Orthorhombic a¼ 0.816, b¼ 1.015,c¼ 0.6823
Fe3C
Ca3Hg2 Tetragonal a¼ 0.8476, c¼ 0.4197 U3Si2Ca5Hg3 Tetragonal a¼ 0.8183, c¼ 1.470 Cr5B3
Ca11–xHg54–x Hexagonal a¼ 1.339, c¼ 0.9615
G. Bruzzone and F. Merlo, The calcium–mercury system, J. Less-CommonMet., 1973, 32, 237–241.
A. V. Tkachuk and A. Mar, Alkaline-earth metal mercury intermetallicsA11�xHg541x (A¼Ca, Sr), Inorg. Chem., 2008, 47, 1313–1318.
Cd–Hg
Phase Crystal structureLatticeparameters (nm)
Density(g cm–3) Prototype
o 29–98%Hg Body-centeredtetragonal
a¼ 0.3965,c¼ 0.2869
In
o0 33–42%Hg(Cd2Hg)
Body-centeredtetragonal
a¼ 0.3965,c¼ 0.8607
MoSi2
o0 58–71%Hg(CdHg2)
Body-centeredtetragonal
a¼ 0.3966,c¼ 0.8607
MoSi2
T. Claeson, H. L. Luo, T. R. Anatharaman and M. E. Merriam,Order–disorder transformations at 2:1 composition in the Cd–Hg system,Acta Metall., 1996, 14, 285–290.
R. Kubiak, A. Pietraszko and K. Lukaszewicz, X-ray investigation ofCd65Hg35 and Cd55Hg45, Acta Crystallogr. A, 1978, 34, S179.
B. Predel andW. Schwermann, Order–disorder transition in the Cd–Hg system,J. Inst. Met., 1971, 99, 209–212.
V. V. Prytkin, L. M. Lityagina and E. V. Biblik, The effect of temperature andpressure on the lattice parameters of the o-phase in the Cd–Hg system,Metallofizika, 1986, 8, 76–80.
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Ce–Hg
Phase Crystal structure Lattice parameters (nm) Density (g cm–3) Prototype
CeHg Cubic a¼ 0.3816 CsClCeHg2 Trigonal a¼ 0.4942, c¼ 0.3540 CeCd2CeHg3 Hexagonal a¼ 0.6755, c¼ 0.4957 Ni3SnCe11Hg45 Cubic a¼ 2.1857 Sm11Cd45
A. Iandelli and A. Palenzona, Crystal chemistry of intermetallic compounds, inHandbook on the Physics and Chemistry of Rare Earths, ed. K. A. GschneidnerJr and L Eyring, North-Holland, Amsterdam, 1979, pp. 1–54.
F. Merlo and M. L. Fornasini, Crystal structure of the R11Hg45 compounds(R¼La, Ce, Pr, Nd, Sm, Gd, Yb, U), J. Less-Common Met., 1979, 64,221–231.
Cl–Hg
Phase Crystal structure Lattice parameters (nm)Density(g cm–3) Prototype
a-Hg2Cl2b-Hg2Cl2 a¼ 0.4482, c¼ 1.091 bHg2Cl2g-Hg2Cl2 Orthorhombic a¼ 0.423, b¼ 0.454, c¼ 1.044HgCl2 a¼ 1.2768, b¼ 0.59756, c¼ 0.43347 PbCl2
N. J. Calos, C. H. L. Kermard and D. R. Lindsay, The structure of Hg2Cl2derived from neutron powder data, Z. Kristallogr., 1989, 187, 305–307.
E. Dorm, Intermetallic distances in Hg(I) halides Hg2F2, Hg2Cl2, Hg2Br2,J. Chem. Soc., Chem. Commun., 1971, 466–467.
C. Guminski, The Cl–Hg (chlorine–mercury) system, J. Phase Equilib., 1994,15, 101–107.
V. Subramamian and K. Serf, HgCl2, a redetermination, Acta Crystallogr.B, 1980, 36, 2132–2135.
S. J. Yosim and S. W. Mayer, The Hg–HgCl2 system, J. Phys.Chem. Solids,1960, 64, 909–911.
Cs–Hg
PhaseCrystalstructure Lattice parameters (nm)
Density(g cm–3) Prototype
Cs2Hg27 Cubic a¼ 1.6557 12.47calc Cs2Hg27Cs3Hg2 Cubic a¼ 1.0913 11.27calc Cs3Hg20Cs5Hg1 Tetragonal a¼ 1.1803, c¼ 1.0814 9.87calc Rb5Hg19CsHg Orthorhombic a¼ 0.8727, b¼ 0.5488, c¼ 0.9082 8.19 KHg2CsHg Triclinic a¼ 0.7154, b¼ 0.7470, c¼ 0.7635
a¼ 107.821, b¼ 103.341, g¼ 90.9515.91 KHg
H.-J. Deiseroth and A. Strunck, Square Hg4 clusters in the compound CsHg,Angew. Chem. Int. Ed. Engl., 1987, 26, 687–688.
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H.-J. Deiseroth, A. Strunck and W. Bauhofer, RbHg2 and CsHg2 –preparation, crystal structures and electrical conductivities, Z. Anorg. Allg.Chem., 1988, 558, 128–136.
H.-J. Deiseroth, A. Strunck and W. Bauhofer, CsHg, an unusual variant of theCsCl structure. Preparation, crystal structure and physical properties, Z.Anorg. Allg. Chem., 1989, 575, 31.
C. Hoch and A. Simon, Cs2Hg27, the mercury-richest amalgam with closerelationship to the Bergman phases, Z. Anorg. Allg. Chem., 2008, 634,853–856.
E. Todorov and S. C. Sevov, Synthesis and structure of the alkali-metalamalgams A3Hg20 (A¼Rb, Cs), K3Hg11, Cs5Hg19 and A7Hg31 (A¼K, Rb),J. Solid State Chem., 2000, 149, 419–427.
Cu–Hg
Phase Crystal structure Lattice parameters (nm) Density (g cm–3) Prototype
Cu7Hg6 Rhombohedral a¼ 0.94024a¼ 90.4251
H. J. Bernhardt and K. Schmetzer, Belendorffite, a new copper amalgamdimorphous with kolymite, Neues Jahrb. Mineral. Monatsh., 1992, (1),21–28.
M. M. Carnasciali and G. A. Costa, CuxHgy: a puzzling compound, J. AlloysCompd., 2001, 317–318, 491–496.
T. Lindahl and S. Westman, Structure of rhombohedral g brass-like phase inCu–Hg system, Acta Chem. Scand., 1969, 23, 1181–1190.
E. A. Markova, N. M. Chernitsova, Yu. S. Borodaev, L. S. Dubakina and O.E. Yushko-Zakharova, The new mineral kolymite, Cu7Hg6, Int. Geol. Rev.,1982, 24, 233–237.
Dy–Hg
Phase Crystal structure Lattice parameters (nm) Density (g cm–3) Prototype
DyHg Cubic a¼ 0.3676 CsClDyHg2 Trigonal a¼ 0.4816, c¼ 0.3466 CeCd2DyHg3 Hexagonal a¼ 0.6543, c¼ 0.4880 Ni3Sn
A. Iandelli and A. Palenzona, Atomic size of rare earths in intermetalliccompounds, MX compounds of CsCl type, J. Less-Common Met., 1965, 9,1–6.
A. Iandelli and A. Palenzona, Crystal chemistry of intermetallic compounds, inHandbook on the Physics and Chemistry of Rare Earths, ed. K. A.Gschneidner Jr and L Eyring, North-Holland, Amsterdam, 1979, pp. 1–54.
A. Palenzona, MX3 intermetallic phase of the rare earths with Hg, In, Tl, Pb,J. Less-Common Met., 1966, 10, 290–292.
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Er–Hg
Phase Crystal structure Lattice parameters (nm) Density (g cm–3) Prototype
ErHg Cubic a¼ 0.3645 CsClErHg2 Trigonal a¼ 0.4790, c¼ 0.3442 CeCd2ErHg3 Hexagonal a¼ 0.6505, c¼ 0.4866 Ni3Sn
A. Iandelli and A. Palenzona, Atomic size of rare earths in intermetalliccompounds, MX compounds of CsCl type, J. Less-Common Met., 1965,9, 1–6.
A. Palenzona, MX3 intermetallic phase of the rare earths with Hg, In, Tl, Pb, J.Less-Common Met., 1966, 10, 290–292.
Eu–Hg
Phase Crystal structure Lattice parameters (nm) Density (g cm–3) Prototype
EuHg Cubic a¼ 0.3880 CsClEuHg2 Trigonal a¼ 0.4978, c¼ 0.3710 CeCd2EuHg3 Hexagonal a¼ 0.6794, c¼ 0.5074 Ni3SnEu14Hg51 Hexagonal a¼ 1.357, c¼ 0.974 Gd14Ag51
D. M. Bailey and G. R. Kline, Acta Crystallogr. B, 1971, 27, 650.S. J. Lyle and W. A. Westal, A Mossbauer spectroscopic study of the Eu–Hgsystem, J. Less-Common Met., 1984, 99, 265–272.
A. Iandelli and A. Palenzona, Atomic size of rare earths in intermetalliccompounds, MX compounds of CsCl type, J. Less-Common Met., 1965, 9,1–6.
A. Iandelli and A. Palenzona, Crystal chemistry of intermetallic compounds, inHandbook on the Physics and Chemistry of Rare Earths, ed. K. A.Gschneidner Jr and L Eyring, North-Holland, Amsterdam, 1979,pp. 1–54.
F–Hg
Phase Crystal structure Lattice parameters (nm) Density (g cm–3) Prototype
Hg2F2 a¼ 0.3673, c¼ 1.0884 CaF2
HgF2 a¼ 0.55373
E. Dorm, J. Chem. Soc., Chem. Commun., 1971, 466–467.H. E. Swanson, M. C. Morris, R. P. Stinchfield and E. H. Evans, StandardX-Ray Diffraction Powder Patterns, NBSMonograph 25, National Bureau ofStandards, Gaithersburg, MD, 1963, Sect. 2, p. 25.
Ga–Hg
No intermetallic compounds.
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Gd–Hg
Phase Crystal structure Lattice parameters (nm) Density (g cm–3) Prototype
GdHg Cubic a¼ 0.3719 CsClGdHg2 Trigonal a¼ 0.4854, c¼ 0.3496 CeCd2GdHg3 Hexagonal a¼ 0.6591, c¼ 0.4889 Ni3SnGd14Hg51 Hexagonal Gd14 Ag51Gd11Hg45 Cubic a¼ 2.1551 Sm11Cd45
C. Guminski, The Gd–Hg (gadolinium–mercury) system, J. Phase Equilib.,1995, 16, 181–185.
A. Iandelli, Intermetallic and metalloid Gd compounds, An. Accad. Naz. LinceiRend. Cl. Sci. Fis. Mat. Nat., 1960, 29, 62–69.
A. Iandelli and A. Palenzona, Crystal chemistry of intermetallic compounds,in Handbook on the Physics and Chemistry of Rare Earths, ed. K. A.Gschneidner Jr and L Eyring, North-Holland, Amsterdam, 1979,pp. 1–54.
H. R. Kirchmayr, Compounds of Y, Sm and Gd with Hg, Acta Phys.Austriaca, 1964, 18, 193–204.
F. Merlo and M. L. Fornasini, Crystal structure of the R11Hg45 compounds(R¼La, Ce, Pr, Nd, Sm, Gd, Yb, U), J. Less-Common Met., 1979, 64,221–231.
A. Palenzona, MX3 intermetallic phase of the rare earths with Hg, In, Tl, Pb,J. Less-Common Met., 1966, 10, 290–292.
Hf–Hg
Phase Crystal structure Lattice parameters (nm) Density (g cm–3) Prototype
Hf2Hg Tetragonal a¼ 0.3345, c¼ 1.1496 MoSi2
F. Kurka and P. Ettmayer, Die Kristallstruktur von Hf2Hg, Monatsh. Chem.,1967, 98, 2414–2418.
Ho–Hg
Phase Crystal structure Lattice parameters (nm) Density (g cm–3) Prototype
HoHg Cubic a¼ 0.3660 CsClHoHg2 Trigonal a¼ 0.4798, c¼ 0.3470 CeCd2HoHg3 Hexagonal a¼ 0.6526, c¼ 0.4872 Ni3Sn
A. Iandelli and A. Palenzona, Atomic size of rare earths in intermetalliccompounds, MX compounds of CsCl type, J. Less-Common Met., 1965, 9,1–6.
A. Iandelli and A. Palenzona, Crystal chemistry of intermetallic compounds,in Handbook on the Physics and Chemistry of Rare Earths, ed. K. A.Gschneidner Jr and L Eyring, North-Holland, Amsterdam, 1979,pp. 1–54.
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H. R. Kirchmayr, Lattice constants and structures of compounds HoHg,HoHg2 and HoHg3, Monatsh. Chem., 1964, 95, 1667–1670.
A. Palenzona, MX3 intermetallic phase of the rare earths with Hg, In, Tl, Pb, J.Less-Common Met., 1966, 10, 290–292.
I–Hg
Phase Crystal structure Lattice parameters (nm) Density (g cm–3) Prototype
Hg2I2 a¼ 0.4924, c¼ 1.1633 Hg2Cl2a-HgI2 a¼ 0.4374, c¼ 1.2435b-HgI2 a¼ 0.4702, b¼ 0.7432,
c¼ 1.3872HgBr2
g-HgI2 a¼ 0.422, c¼ 2.370
H. Oppermann, On the constitution barogram of the HgI2–I2 system, Z. Anorg.Allg. Chem., 1989, 576, 229–234.
C. Guminski, The Hg–I (mercury–iodine) system, J. Phase Equilib., 1997, 18,206–215.
In–Hg
Phase Crystal structure Lattice parameters (nm) Density (g cm–3) Prototype
e 78–94at.%
Face-centeredcubic
a¼ 0.4694 Cu
In2HgInHg Rhombohedral a¼ 0.4846
a¼ 43.241CuPt–L11
InHg4 Face-centeredorthorhombic
a¼ 1.0872, b¼ 0.4847,c¼ 0.3522
g-Pu
T. Claeson and M. F. Merriam, New phase in the mercury–indium system, J.Less-Common Met., 1966, 11, 186–190.
B. R. Coles, M. F. Merriam and Z. Fisk, The phase diagram of themercury–indium alloy system, J. Less-Common Met., 1963, 5, 41–48.
T. X. Mahy and B. C. Giessen, A new representative of the g-Pu structure type:the crystal structure of b(Hg0.80In0.20), J. Less-Common Met., 1979, 63,257–264.
H. Okamoto, Phase Diagrams of Binary Indium Alloys, ASM, Metals Park,OH, 1991, p. 129.
M. Segnini and B. C. Giessen, The crystal structure of HgIn, Acta Crystallogr.B, 1972, 28, 320–321.
C. Tyzack and G. V. Raynor, Trans. Faraday Soc., 1954, 50, 675–684.
K–Hg
Phase Structure Lattice parameters (nm) Density (g cm–3) Prototype
KHg11 Cubic a¼ 0.9630 12.46calc BaHg11K3Hg11 a¼ 0.5122, b¼ 1.0063,
c¼ 1.478210.13calc a-La3Al11
256 Appendix I
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Phase Structure Lattice parameters (nm) Density (g cm–3) Prototype
KHg6 OrthorhombicKHg7K7Hg31 Hexagonal a¼ 1.0850 m, c¼ 1.0210 10.36calc Ba7Hg31K2Hg7 Hexagonal a¼ 0.67175, c¼ 0.64133 K2Hg7a-KHg2 Orthorhombic a¼ 0.810, b¼ 0.516,
c¼ 0.8777.88calc, 7.95meas KHg2
b-KHg2 Mod. AlB2
K29Hg48 CubicK5Hg7 Orthorhombic a¼ 1.006, b¼ 1.945,
c¼ 0.834K5Hg7
KHg Triclinic a¼ 0.659, b¼ 0.676,c¼ 0.706
a¼ 106150, b¼ 1011520,g¼ 921470
5.41calc, 5.47meas KHg
E. Biehl, Thesis, University of Siegen, 1998.E. Biehl and H.-J. Deiseroth, Preparation, structural relations and magnetismof amalgams MHg11 (M: K, Rb, Ba, Sr), Z. Anorg. Allg. Chem., 1999, 625,1073–1080.
E. Biehl, H.-J. Deiseroth, K2Hg7 und Rb2Hg7, zwei Vertreter eines neuenStrukturtyps binarer intermetallischer Verbindungen, Z. Anorg. Allg. Chem.,1999, 625, 1337–1342.
H.-J. Deiseroth, Alkali metal amalgams: a group of unusual alloys, Prog. SolidState Chem., 1997, 25, 73–123.
E. J. Duwell and N. C. Baenziger, The crystal structures of KHg and KHg2,Acta Crystallogr., 1955, 8, 705.
E. J. Duwell and N. C. Baenziger, The crystal structure of K5Hg7, ActaCrystallogr., 1960, 13, 476–479.
E. Maey, Z. Phys. Chem., 1899, 29, 119–138.E. Todorov and S. C. Sevov, Synthesis and structure of the alkali-metalamalgams A3Hg20 (A¼Rb, Cs), K3Hg11, Cs5Hg19 and A7Hg31 (A¼K, Rb),J. Solid State Chem., 2000, 149, 419–427.
La–Hg
Phase Crystal structure Lattice parameters (nm) Density (g cm–3) Prototype
LaHg Cubic a¼ 0.3864 CsClLaHg2 Trigonal a¼ 0.4960, c¼ 0.3650 CeCd2LaHg3 Hexagonal a¼ 0.6816, c¼ 0.4971 12.30calc Ni3SnLa11Hg45 Cubic a¼ 2.1997 g-BrassLa13Hg58 Hexagonal a¼ 1.567, c¼ 1.548 Pu13Zn58LaHg6 Orthorhombic a¼ 0.9763, b¼ 2.886,
c¼ 0.5004
G. Bruzzone and F. Merlo, The lanthanum–mercury system, J. Less-CommonMet., 1976, 44, 259–265.
C. Guminski, The La–Hg (lanthanum–mercury) system, J. Phase Equilibria,1995, 16, 86–192.
Phase Diagrams and Intermetallic Compounds in Binary Amalgam Systems 257
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A. Iandelli and A. Palenzona, Crystal chemistry of intermetallic compounds, inHandbook on the Physics and Chemistry of Rare Earths, ed. K. A.Gschneidner Jr and L Eyring, North-Holland, Amsterdam, 1979, pp. 1–54.
F. Merlo and M. L. Fornasini, Crystal structure of the R11Hg45 compounds(R¼La, Ce, Pr, Nd, Sm, Gd, Yb, U), J. Less-Common Met., 1979, 64,221–231.
Li–Hg
PhaseCrystalstructure
Latticeparameters (nm) Density (g cm–3) Prototype
LiHg3 Hexagonal a¼ 0.6253,c¼ 0.4804
Ni3Sn
LiHg2LiHg (38–62 at.% Li at375 1C)
Cubic a¼ 0.3315 9.28meas (52.1at.% Li)
CsCl
Li3Hg Cubic a¼ 0.6548 Li3Bi
G. Grube and W. Wolf, Z. Elektrochem., 1935, 41, 675–679.E. Zintl and A. Schneider, Rontgenanalyse der Lithium-Amalgame,Z. Elektrochem., 1935, 41, 771–774.
E Zintl and G. Brauer, Z. Phys. Chem., 1933, B20, 245–271.G. J. Zukowsky, Z. Anorg. Allg. Chem., 1911, 71, 403–418.
Lu–Hg
Phase Crystal structure Lattice parameters (nm) Density (g cm–3) Prototype
LuHg Cubic a¼ 0.3607 CsClLuHg3 Hexagonal a¼ 0.6467, c¼ 0.4851 Ni3Sn
C. Guminski, The Hg–Lu (mercury–lutetium) system, J. Phase Equilib., 1995,16, 276.
A. Iandelli and A. Palenzona, Atomic size of rare earths in intermetalliccompounds, MX compounds of CsCl type, J. Less-Common Met., 1965, 9, 1–6.
A. Iandelli and A. Palenzona, Crystal chemistry of intermetallic compounds, inHandbook on the Physics and Chemistry of Rare Earths, ed. K. A. GschneidnerJr and L Eyring, North-Holland, Amsterdam, 1979, pp. 1–54.
A. Palenzona, MX3 intermetallic phase of the rare earths with Hg, In, Tl, Pb, J.Less-Common Met., 1966, 10, 290–292.
Mg–Hg
PhaseCrystalstructure Lattice parameters (nm) Density (g cm–3) Prototype
Mg3Hg Hexagonal a¼ 0.483, c¼ 0.862 Na3AsMg5Hg2Mg2Hg Orthorhombic a¼ 0.6219, b¼ 0.4617,
c¼ 0.8799CoSi2
258 Appendix I
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PhaseCrystalstructure Lattice parameters (nm) Density (g cm–3) Prototype
Mg5Hg3 Hexagonal a¼ 0.8260, c¼ 0.5931 Mn5Si3MgHg Cubic a¼ 0.3449 CsClMgHg2 a¼ 0.3838, c¼ 0.8799 MoSi2
G. Brauer and W. Hauke, Crystal structure of intermetallic compounds MgAuand MgHg, Z. Phys. Chem. B, 1936, 33, 304–310.
G. Brauer and R. Rudolph, X-ray analysis of magnesium amalgams, Z. Anorg.Chem., 1941, 248, 405–524.
G. Brauer, H. Nowotny and R. Rudolph, X-ray investigation of the Mg–Hgsystem, Z. Metallkd., 1947, 38, 81–84.
J. L. C. Daams and J. H. N. van Vucht, The Mg–Au–Hg system, Philips J. Res.,1984, 39, 275–292.
A. A. Nayeb-Hashemi and J. B. Clark, The Hg–Mg (mercury–magnesiumsystem), J. Phase Equilib., 1987, 8, 65–70.
Mn–Hg
Phase Crystal structure Lattice parameters (nm) Density (g cm–3) Prototype
a-MnHg Cubic a¼ 0.3318 CsClb-MnHg Tetragonal a¼ 0.3298, c¼ 0.3912 MnHgg-MnHgMn2Hg5 Tetragonal a¼ 0.9758, c¼ 0.2998 12.85meas, 13.00calc Mn2Hg5
J. E. deWet, Intermetallic phases in the Mn–Hg system, Angew. Chem., 1955,67, 208.
J. E deWet, A new metallic layer structure, Nature, 1957, 180, 1412–1413.J. E deWet, Crystal structure of Mn2Hg5, Acta Crystallogr., 1961, 14, 733–738.E. Lihl, Investigations on the amalgams of Mn, Fe, Co, Ni and Cu,Z. Metallkd., 1953, 44, 160–166.
E. Lihl, On the structure of the Hg–Mn system, Monatsh. Chem., 1955, 86,186–190.
Z. Moser and C. Guminski, The Hg–Mn system, J. Phase Equilib., 1993, 14,726–733.
M. Ohashi, The magnetic and thermal properties of the intermetalliccompound MnHg, J. Phys. Soc. Jpn., 1965, 20, 911–914.
Na–Hg
Phase Crystal structure Lattice parameters (nm)Density(g cm–3) Protoype
Na11Hg52 Hexagonal a¼ 3.9703, c¼ 0.96810 12.04calc Na11Hg52NaHg2 Hexagonal a¼ 0.5029, c¼ 0.3230 9.96calc,
9.94measModifiedAlB2
a-NaHg End-centeredorthorhombic
a¼ 0.7184, b¼ 1.0784,c¼ 0.5198
DistortedCsCl
Phase Diagrams and Intermetallic Compounds in Binary Amalgam Systems 259
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Phase Crystal structure Lattice parameters (nm)Density(g cm–3) Protoype
b-NaHg Rhombohedral a¼ 0.5071, c¼ 1.2668 DistortedNaTl
g-NaHg Cubic a¼ 0.5129 NaTlNa3Hg2 Tetragonal a¼ 0.84587, c¼ 0.77078 5.66calc Na3Hg2a-Na8Hg3 Hexagonal a¼ 0.5433, c¼ 0.7795 Au8Al3b-Na8Hg3 Monoclinic a¼ b¼ c¼ 0.7676
b¼ 90.71DistortedLi3Bi
g-Na8Hg3 Cubic a¼ 0.7674 Li3Bia-Na3Hg Hexagonal a¼ 0.5438, c¼ 0.9808 3.56calc
(34 1C)Na3As
b-Na3Hg Rhombohedral a¼ 0.5404, c¼ 1.3420 3.95calc
(42 1C)ModifiedLi3Bi
H.-J. Deiseroth and M. Rochnia, Temperature dependent phasetransitions of sodium-rich amalgams, Z. Anorg. Allg. Chem., 1992, 616,35–38.
H.-J. Deiseroth and M. Rochnia, b-Na3Hg: a solid with a quasi-fluid sodiumsubstructure between 36 and 60 1C, Angew. Chem. Int. Ed. Engl., 1993, 32,1494–1495.
H.-J. Deiseroth and M. Rochnia, Temperature-dependent phase con-versions of sodium-rich amalgams, Z. Anorg. Allg. Chem., 1994, 620,1736–1740.
H.-J. Deiseroth and D. Toelstede, Na8Hg3: an alkali metal richamalgam with isolated mercury anions?, Z. Anorg. Allg. Chem., 1990, 587,103–109.
H.-J. Deiseroth and D. Toelstede, Na3Hg – the most sodium-richamalgam in the system sodium–mercury, Z. Anorg. Allg. Chem., 1992, 615,43–48.
H.-J. Deiseroth, A. Stupperich, R. Pankaluoto and N. E. Christensen, NaHg: avariant of the cesium chloride structure – structural relations and electronicstructure, Z. Anorg. Allg. Chem., 1991, 597, 41–50.
H.-J. Deiseroth, E. Biehl and M. Rochnia, Sodium amalgams: phase diagram,structural chemistry and thermodynamic data, a summary of recent devel-opments, J. Alloys Compd., 1997, 246, 80–90.
C. Hoch and A. Simon, Na11Hg52: complexity in a polar metal, Angew. Chem.Int. Ed., 2012, 51, 3262–3265.
E. Maey, Z. Phys. Chem., 1899, 29, 119.J. W. Nielsen and N. C. Baenziger, The crystal structures of NaHg2, NaHg andNa3Hg2, Acta Crystallogr., 1954, 7, 277–282.
M. Rochnia and H.-J. Deiseroth, Polymorphism of NaHg: the firstexperimental observation of a reversible, temperature driven B2(CsCl)–B32 (NaTl) phase transition, Croat. Chem. Acta, 1995, 68,701–708.
A. V. Tkachuk and A. Mar, Redetermination of Na3Hg2, Acta Crystallogr. E,2006, 62, i129–i130.
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Nd–Hg
Phase Crystal structure Lattice parameters (nm) Density (g cm–3) Prototype
NdHg Cubic a¼ 0.3780 CsClNdHg2 Trigonal a¼ 0.4904, c¼ 0.3520 CeCd2NdHg3 Hexagonal a¼ 0.6695, c¼ 0.4929 Ni3SnNd11Hg45 Cubic a¼ 2.1716 Sm11Cd45
C. Guminski, The Hg–Nd (mercury–neodymium) system, J. Phase Equilibria,1995, 16, 448–453.
A. Iandelli and A. Palenzona, Crystal chemistry of intermetallic compounds, inHandbook on the Physics and Chemistry of Rare Earths, ed. K. A. GschneidnerJr and L Eyring, North-Holland, Amsterdam, 1979, pp. 1–54.
F. Merlo and M. L. Fornasini, Crystal structure of the R11Hg45 compounds(R¼La, Ce, Pr, Nd, Sm, Gd, Yb, U), J. Less-Common Met., 1979, 64,221–231.
Ni–Hg
Phase Crystal structure Lattice parameters (nm) Density (g cm–3) Protoype
NiHg Tetragonal a¼ 0.422, c¼ 0.314 AuCuNiHg2 Tetragonal a¼ 0.456, c¼ 0.283 PtHg2NiHg3 Cubic a¼ 0.3005NiHg4 Cubic a¼ 0.3004 PtHg4
A Baranski and Z. Galus, An electrochemical study of the equilibria in thenickel–mercury system, J. Electroanal. Chem. Interfacial Electrochem., 1973,46, 289–305.
L. F. Bates and J. H. Prentice, Proc. Phys. Soc., 1939, 51 419.F. Lihl, Investigation of the amalgams of the metals manganese, iron, cobalt,nickel and copper, Z. Metallkd., 1953, 44, 160.
F. Lihl and H. Nowotny, The structure of NiHg4, Z. Metallkd., 1953, 44, 358–360.M. Puselj and Z. Ban, Preparation and crystal structure of NiHg,Z. Naturforsch., 1977, 32B, 497.
O–Hg
Phase Crystal structure Lattice parameters (nm)Density(g cm–3) Prototype
HgO Triclinic a¼ 0.665, b¼ 0.554, c¼ 0.701a¼ 90.151, b¼ 90.451, g¼ 90.951
HgO
HgO Orthorhombic a¼ 0.66074, b¼ 0.55254,c¼ 0.35215
HgO
HgO Tetragonal a¼ 0.82941, b¼ 0.71121HgO Cubic a¼ 0.534 ZnSHgO Hexagonal a¼ 0.3578, c¼ 0.8685 HgSa-HgO2 Rhombohedral a¼ 0.44702, b¼ 0.54592,
c¼ 0.35192b¼ 108.451
a-HgO2
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Phase Crystal structure Lattice parameters (nm)Density(g cm–3) Prototype
b-HgO2 a¼ 0.608, b¼ 0.601, c¼ 0.480 b-HgO2
Hg2O Decomposes at100 1C
C. Guminski, The Hg–O (mercury-oxygen) system, J. Phase Equilib., 1999, 20,85–88.
Pb–Hg
Phase Crystal structure Lattice parameters (nm) Density (g cm–3) Prototype
Pb2Hg Face-centeredtetragonal
a¼ 0.3520, c¼ 0.4512 CuAu
M. Ellner and B. Predel, The structure of TlSn(h) and its crystal chemicalrelationship to similar phases, Z. Metalkd., 1975, 66, 503–506.
C. Tyzack and G. V. Raynor, The lattice spacings of Pb-rich substitutionalsolid solutions, Acta Crystallogr., 1954, 7, 505–510.
Pd–Hg
Phase Crystal structure Lattice parameters (nm) Density (g cm–3) Prototype
PdHg4 orPd5Hg21
Complexg-brass
Pd2Hg5 Tetragonal a¼ 0.9463, c¼ 0.3031 Mn2Hg5PdHg Tetragonal a¼ 0.3026, c¼ 0.3702 AuCu
A. Baranski, A. Kryska and Z. Galus, On the electrochemical properties of thePdþHg system, J. Electroanal. Chem., 1993, 349, 341–354.
H. Bittner and H. Nowotny, Investigation of the system Pd–Hg, Monatsh.Chem., 1952, 83, 287–288.
H. Bittner and H. Nowotny, Further magnetic measurements ofHume–Rothery phases, Monatsh. Chem., 1952, 83, 1308–1313.
J. D. Cummins and A. F. Berndt, A single crystal study of Pd–Hg andg-Sn–Hg, J. Less-Common Met., 1969, 19, 431–432.
P. Ettmayer, Die Kristallstruktur von Pd2Hg5, Monatsh. Chem., 1965, 96,884–888.
K. Terada and F. W. Cagle Jr, The solid solution of mercury in palladium, ActaCrystallogr., 1961, 14, 1299.
Po–Hg
Phase Crystal structure Lattice parameters (nm) Density (g cm–3) Prototype
PoHg Ordered fcc a¼ 0.6250 NaCl
W. G. Witteman, A. L. Giorgi and D. T. Vier, The preparation and identifi-cation of some intermetallic compounds of polonium, J. Phys. Chem., 1960,64, 434–440.
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Pr–Hg
Phase Crystal structure Lattice parameters (nm) Density (g cm–3) Prototype
PrHg Cubic a¼ 0.3799 CsClPrHg2 Trigonal a¼ 0.4918, c¼ 0.3539 CeCd2PrHg3 Hexagonal a¼ 0.6724, c¼ 0.4937 Ni3SnPr11Hg45 Cubic a¼ 2.1786 Sm11Cd45
A. Iandelli and A. Palenzona, Crystal chemistry of intermetallic compounds, inHandbook on the Physics and Chemistry of Rare Earths, ed. K. A.Gschneidner Jr and L Eyring, North-Holland, Amsterdam, 1979,pp. 1–54.
F. Merlo and M. L. Fornasini, Crystal structure of the R11Hg45 compounds(R¼La, Ce, Pr, Nd, Sm, Gd, Yb, U), J. Less-Common Met., 1979, 64,221–231.
Pt–Hg
Phase Crystal structureLatticeparameters (nm)
Density(g cm–3) Prototype
PtHg4 Body-centered cubic a¼ 0.61808 PtHg4PtHg2 Tetragonal a¼ 0.4675, c¼ 0.2918 15.6calc PtHg2PtHg Tetragonal a¼ 0.4193, c¼ 0.3817 AuCu (L10)
E. Bauer, H. Nowotny and A. Stempfl, X-ray investigation in the Pt–Hgsystem, Monatsh. Chem., 1953, 84, 211–212.
E. Bauer, H. Nowotny and A. Stempfl, X-ray investigation in the Pt–Hgsystem, Monatsh. Chem., 1953, 84, 692–700.
S. K. Lahiri, J. Angilello and M. Natan, Precise lattice parameter deter-mination of PtHg4, J. Appl. Crystallogr., 1982, 15, 100–101.
G. D. Robbins and C. G. Enke, Investigation of the compound formed at aPt–Hg interface, J. Electroanal. Chem., 1969, 23, 343–349.
G. R. Souza, I. A. Pastre, A. V. Benedetti, C. A. Ribeiro and F. L. Fertonani,Solid state reactions in the platinum–mercury system, J. Thermal Anal.Calorim., 2007, 88, 127–132.
Pu–Hg
Phase Crystal structure Lattice parameters (nm)Density(g cm–3) Prototype
Pu5Hg21 orPu11Hg45
Cubic a¼ 2.178 13.90calc g-Brass orSm11Cd45
PuHg3 Hexagonal ProbablyNi3Sn
A. F. Berndt, A gamma phase in the Pu–Hg system, J. Less-Common Met.,1966, 11, 216–219.
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A. S. Coffinberry and F. H. Ellinger, Intermetallic compounds of Pu, inPeaceful Uses of Atomic Energy, United Nations, New York, 1956, vol. 9, pp.138–146.
C. Guminski, The Hg–Pu system, J. Equil. Diagr. Diffusion, 2005, 26, 77–79.
Rb–Hg
Phase StructureLatticeparameters (nm)
Density(g cm–3) Prototype
RbHg Triclinic KHgRbHg11 Cubic a¼ 0.9707 12.48calc BaHg11Rb3Hg20 Cubic a¼ 1.0737 11.45calc
RbHg2 Orthorhombic a¼ 0.8449, b¼ 0.5300,c¼ 0.8981
8.06 KHg2
Rb7Hg31 K7Hg31Rb15Hg16 Tetragonal a¼ 1.6653, c¼ 1.8134 Rb15Hg16Rb2Hg7 Hexagonal a¼ 0.68436, c¼ 0.65774Rb5Hg19 Tetragonal a¼ 1.1561, c¼ 1.0510 Defect BaAl4
E. Biehl and H.-J. Deiseroth, Rb5Hg19: Eine neue, geordnete Defektvariantedes BaAl4-Strukturtyps, Z. Anorg. Allg. Chem., 1999, 625, 389–394.
E. Biehl and H.-J. Deiseroth, Preparation, structural relations and magnetismof amalgams MHg11 (M: K, Rb, Ba, Sr), Z. Anorg. Allg. Chem., 1999, 625,1073–1080.
E. Biehl and H.-J. Deiseroth, K2Hg7 und Rb2Hg7, zwei Vertreter eines neuenStrukturtyps binarer intermetallischer Verbindungen, Z. Anorg. Allg. Chem.,1999, 625, 1337–1342.
H.-J. Deiseroth and A. Strunck, Hg8 (‘mercubane’) clusters in Rb15Hg16,Angew. Chem. Int. Ed. Engl., 1989, 28, 1251–1252.
H.-J. Deiseroth, A. Strunck and W. Bauhofer, RbHg2 and CsHg2 –preparation, crystal structures and electrical conductivities, Z. Anorg. Allg.Chem., 1988, 558, 128–136.
E. Todorov and S. C. Sevov, Synthesis and structure of the alkali-metalamalgams A3Hg20 (A¼Rb, Cs), K3Hg11, Cs5Hg19 and A7Hg31 (A¼K, Rb),J. Solid State Chem., 2000, 149, 419–427.
Rh–Hg
Phase Crystal structure Lattice parameters (nm)Density(g cm–3) Prototype
RhHg4.63RhHg5RhHg2 Tetragonal a¼ 0.4551, c¼ 0.2998 PtHg2
P. Ettmayer and B. Mathis, Crystal structure of RhHg2,Monatsh. Chem., 1967,58, 505–506.
G. Jangg, R. H. Kirchmayr and H. B. Mathis, Investigations in the Hg–Rhsystem, Z. Metallkd., 1967, 58, 724–726.
264 Appendix I
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H. Nowotny, University of Vienna, unpublished research.E. Y. Yonashiro and F. L. Fertonani, Thermogravimetry applied tothe study of reaction of Hg with Pt–Rh, Thermochim. Acta, 2002, 383,153–160.
S–Hg
Phase Crystal structure Lattice parameters (nm)Density(g cm–3) Prototype
a-HgS Trigonal a¼ 0.41488, c¼ 0.95039 a-HgSb-HgS Cubic a¼ 0.58514 ZnSg-HgS Hexagonal a¼ 0.6861, c¼ 1.4077HgS Cubic a¼ 0.5070 NaCl
P. Auvray and E. Genet, Affinement of the crystal structure of cinnabar a-HgS,Bull. Soc. Fr. Mineral. Cristall., 1973, 96, 218–219.
T. Huang and A. L. Ruoff, Pressure-induced phase transition of HgS, J. Appl.Phys., 1983, 54, 5459–5461.
A. N. Mariano and E. P. Warekois, High pressure phases of some compoundsof groups II–VI, Science, 1963, 142, 672–673.
T. Ohmiya, Thermal expansion and the phase transformation in HgS, J. Appl.Crystallogr., 1974, 7, 396–397.
R. W. Potter II and H. L. Barnes, Phase relations in the binary Hg–S, Am.Mineral., 1978, 63, 1143–1152.
H. E. Swanson, R. K. Fuyat and G. M. Ugrinic, NBS Circ. 539, 1953, IV,17–23.
Sc–Hg
Phase Crystal structure Lattice parameters (nm)Density(g cm–3) Protoype
ScHg Cubic a¼ 0.3480 CsClScHg3 Hexagonal a¼ 0.6356, c¼ 0.4759 MgCd3
E. Laube and H. Nowotny, Die Kristallstrukturen von ScHg, ScHg3, YCd,YHg und YHg3, Monatsh. Chem., 1963, 94, 851–858.
Se–Hg
Phase Crystal structure Lattice parameters (nm)Density(g cm–3) Prototype
a-HgSe Cubic a¼ 0.60864 ZnSb-HgSe Hexagonal a¼ 0.432, c¼ 0.968 HgSg-HgSe Cubic a¼ 0.5360 NaCld-HgSe Body-centered tetragonal a¼ 0.5112, c¼ 0.2721 b-Sn
Phase Diagrams and Intermetallic Compounds in Binary Amalgam Systems 265
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T.-L. Huang and A. L. Ruoff, High-pressure-induced phase transitions ofmercury chalcogenides, Phys. Rev. B, 1985, 31 5976–5983.
A. N. Mariano and E. P. Warekois, High pressure phases of some compoundsof groups II–VI, Science, 1963, 142, 672–673.
H. P. Singh and B. Dayal, Lattice parameters and thermal expansion of ZnTeand HgSe, Acta Crystallogr. A, 1970, 26, 363–364.
Sm–Hg
Phase Crystal structure Lattice parameters (nm) Density (g cm–3) Prototype
SmHg Cubic a ¼ 0.3744 CsClSmHg2 Trigonal a ¼ 0.4877, c ¼ 3.515 CeCd2SmHg3 Hexagonal a ¼ 0.6632, c ¼ 0.4900 Ni3SnSm11Hg45 Cubic a ¼ 2.1651 Sm11Cd45
A. Iandelli and A. Palenzona, Crystal chemistry of intermetallic compounds, inHandbook on the Physics and Chemistry of Rare Earths, ed. K. A.Gschneidner Jr and L Eyring, North-Holland, Amsterdam, 1979,pp. 1–54.
H. R. Kirchmayr, Compounds of Y, Sm and Gd with Hg, Acta Phys.Austriaca, 1964, 18, 193–204.
F. Merlo and M. L. Fornasini, Crystal structure of the R11Hg45 compounds(R¼La, Ce, Pr, Nd, Sm, Gd, Yb, U), J. Less-Common Met., 1979, 64,221–231.
Sn–Hg
Phase Crystal structure Lattice parameters (nm)Density(g cm–3) Prototype
b 95–98% Sn Hexagonal (probably) a¼ 0.32415, c¼ 0.30065g 89–94% Sn Hexagonal a¼ 0.32109, c¼ 0.29888 BiInd 84–87% Sn Orthorhombically
distorted hexagonala¼ 0.5551, b¼ 0.3179,c¼ 0.2983
HgSn4
Y.-W. Yen, J. Grobner, R. Schmid-Fetzer and S. C. Hansen, Thermo-dynamic assessment of the Hg–Sn system, J. Phase Equilib., 2003, 24,151–167.
J. D. Cummins and A. F. Berndt, A single crystal study of palladium–mercuryand g mercury–tin, J. Less-Common Met., 1969, 19, 431–432.
G. V. Raynor and J. A. Lee, The tin-rich intermediate phases in thealloys of tin with cadmium, indium and mercury, Acta Metall., 1954, 2,616–620.
266 Appendix I
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Sr–Hg
Phase Crystal structure Lattice parameters (nm)Density(g cm–3) Protoype
SrHg8 a¼ 1.3328, b¼ 0.49128,c¼ 2.6446
12.98calc SrHg8
SrHg Cubic a¼ 0.3930 CsClSr2HgSr3Hg Orthorhombic a¼ 0.8523, b¼ 1.108,
c¼ 0.7405Fe3C
SrHg3 Heagonal a¼ 0.6906, c¼ 0.5106 Ni3SnSrHg2 Body-centered
orthorhombica¼ 0.4985, b¼ 0.7754,c¼ 0.8550
CeCu2
Sr3Hg2 Tetragonal a¼ 0.8883, c¼ 0.4553 U3Si2Sr13Hg58 Hexagonal a¼ 1.594, c¼ 1.579 Gd13Zn58SrHg11 Cubic a¼ 0.95099 BaHg11Sr11–xHg541x Hexagonal a¼ 1.3602, c¼ 0.9818
E. Biehl and H.-J. Deiseroth, Preparation, structural relations and magnetismof amalgams MHg11 (M: K, Rb, Ba, Sr), Z. Anorg. Allg. Chem., 1999, 625,1073–1080.
G. Bruzzone and F. Merlo, The strontium–mercury system, J. Less-CommonMet., 1974, 35, 153–157.
C. Druska, T. Doert and P. Bottcher, Refinement of the crystal structure ofSr3Hg2, Z. Anorg. Allg. Chem., 1996, 622, 401–404.
C. Guminski, The Hg–Sr system, J. Phase Equilib. Diffus., 2005, 26,81–86.
A. V. Tkachuk and A. Mar, Alkaline-earth metal mercury intermetallicsA11�xHg541x (A¼Ca, Sr), Inorg. Chem., 2008, 47, 1313–1318.
A. V. Tkachuk and A. Mar, In search of the elusive amalgam SrHg8: amercury-rich intermetallic compound with augmented pentagonal prisms,Dalton Trans., 2010, 39, 7132–7135.
Tb–Hg
Phase Crystal structure Lattice parameters (nm)Density(g cm–3) Prototype
TbHg Cubic a¼ 0.3690 CsClTbHg2 Trigonal a¼ 0.4833, c¼ 0.3487 CeCd2TbHg3 Hexagonal a¼ 0.6565, c¼ 0.4887 Ni3SnTb11Hg45 Cubic
C. Guminski, The Hg–Tb (mercury–terbium) system, J. Phase Equilib., 1995,16, 193–196.
A. Iandelli and A. Palenzona, Atomic size of rare earths in intermetalliccompounds, MX compounds of CsCl type, J. Less-Common Met., 1965, 9,1–6.
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A. Iandelli and A. Palenzona, Crystal chemistry of intermetallic compounds, inHandbook on the Physics and Chemistry of Rare Earths, ed. K. A.Gschneidner Jr and L Eyring, North-Holland, Amsterdam, 1979, pp. 1–54.
H. R. Kirchmayr and W. Lugscheider, Structure of Tb–Hg and Yb–Hgsystems, Z. Metallkd., 1968, 59, 296–297.
A. Palenzona, MX3 intermetallic phase of the rare earths with Hg, In, Tl, Pb, J.Less-Common Met., 1966, 10, 290–292.
Te–Hg
Phase Crystal structure Lattice parameters (nm) Density (g cm–3) Prototype
a-HgTe Cubic a¼ 0.6453 ZnSb-HgTe Hexagonal a¼ 0.445, c¼ 0.989 HgSg-HgTe Cubic a¼ 0.583 NaCld-HgTe Body-centered
tetragonala¼ 0.5524, c¼ 0.2973 b-Sn
e-HgTe a¼ 0.3339, b¼ 0.3611,c¼ 0.3284
DistortedCsCl
T.-L. Huang and A. L. Ruoff, High-pressure induced phase transitions ofmercury chalcogenides, Phys. Rev. B, 1983, 31, 5976–5983.
A. N. Mariano and E.P. Warekois, High pressure phases of some compoundsof groups II–VI, Science, 1963, 142, 672–673.
R. C. Sharma, Y. A. Chang and C. Guminski, The Hg–Te system, J. PhaseEquilib., 1995, 16, 338–348.
A. Werner, H. D. Hochheimer, K. Strossner and A. Jayaraman, High pressureX-ray diffraction studies on HgTe and HgS to 20 GPa, Phys. Rev. B, 1983,28, 3330–3334.
Th–Hg
Phase Crystal structure Lattice parameters (nm) Density (g cm–3) Prototype
ThHg3 Hexagonal a¼ 0.6716, c¼ 0.4902 14.39 calc Ni3SnThHg2 Hexagonal a¼ 0.4822, c¼ 0.7438 CaIn2ThHgTh2Hg Tetragonal a¼ 0.7696, c¼ 0.5902 CuAl2
P. Chiotti, V. V. Akhachinskii, I. Ansara and M. H. Rand, The ChemicalThermodynamics of Actinide Elements and Compounds, Part 5, The ActinideBinary Alloys, International Atomic Energy Agency, Vienna, 1981,p. 34.
R. E. Domagala, R. E. Elliott and W. Rostocker, The system Hg–Th, Trans.AIME, 1958, 212, 393–395.
P. Ettmayer, Beitrag zum System Quecksilber–Thorium, Monatsh. Chem.,1965, 96, 443–449.
268 Appendix I
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R. Ferro, The crystal structures of ThHg3, ThIn3, ThTl3, ThSn3 and ThPb3,Acta Crystallogr., 1958, 11, 737–738.
A. Palenzona, Th2Hg: another representative of the CuAl2-type structure,J. Less-Common Met., 1986, 125, L5–L6.
Ti–Hg
Phase Crystal structure Lattice parameters (nm) Density (g cm–3) Protoype
TiHg Tetragonal a¼ 0.3009, c¼ 0.4041 AuCu (L10)g-Ti3Hg Cubic a¼ 0.51888 Cr3Sid-Ti3Hg Cubic a¼ 0.41654 AuCu3 (L12)TiHg3
J. L. Murray, The Hg–Ti System, Phase Diagrams of Binary Ti Alloys, ASM,Metals Park, OH, 1987, p. 140.
P. Pietrokowsky, A cursory investigation of intermediate phases in the systemsTi–Zn, Ti–Hg, Zr–Zn, Zr–Cd and Zr–Hg by X-ray powder diffractionmethod, J. Met., 1954, 6, 219–226.
E. Vielhaber and H. L. Luo, Solid State Commun., 1967, 5, 221–223.
Tl–Hg
Phase Crystal structureLattice parameters(nm)
Density(g cm–3) Prototype
g-(Hg5Tl2) 20–30%Tl
Face-centeredcubic
a¼ 0.4628–0.468 Cu
W. Gierlotka, J. Sopousek and K. Fitzner, Thermodynamic assessment of theHg–Tl system, CALPHAD, 2006, 30, 425–430.
R. St. Amand and B. C. Giessen, On the metastable system Hg–Tl, J. Less-Common Met., 1978, 58, 161–172.
Tm–Hg
Phase Crystal structure Lattice parameters (nm) Density (g cm–3) Prototype
TmHg Cubic a¼ 0.3632 CsClTmHg3 Hexagonal a¼ 0.6491, c¼ 0.4856 Ni3Sn
C. Guminski, The Hg–Tm (mercury–thulium) system, J. Phase Equilib., 1995,16, 459.
A. Iandelli and A. Palenzona, Atomic size of rare earths in intermetallic compounds,MX compounds of CsCl type, J. Less-Common Met., 1965, 9, 1–6.
A. Iandelli and A. Palenzona, Crystal chemistry of intermetallic compounds, inHandbook on the Physics and Chemistry of Rare Earths, ed. K. A. GschneidnerJr and L Eyring, North-Holland, Amsterdam, 1979, pp. 1–54.
A. Palenzona, MX3 intermetallic phase of the rare earths with Hg, In, Tl, Pb, J.Less-Common Met., 1966, 10, 290–292.
Phase Diagrams and Intermetallic Compounds in Binary Amalgam Systems 269
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U–Hg
Phase Crystal structure Lattice parameters (nm) Density (g cm–3) Prototype
UHgUHg2 Hexagonal a¼ 0.4976, c¼ 0.3218 AlB2
UHg3 Hexagonal a¼ 0.3320, c¼ 0.4875 14.88calc Ni3SnU11Hg45 Cubic a¼ 2.1720 Sm11Cd45
B. R. T. Frost, The U–Hg system, J. Inst. Met., 1953–54, 82, 456–462.C. Guminski, The Hg–U system, J. Phase Equilib., 2003, 24, 461–468.T. S. Lee, P. Chiotti and J. T. Mason, Phase relations in the U–Hg system,J. Less-Common Met., 1979, 66, 33–40.
F. Merlo and M. L. Fornasini, Crystal structure of the Hg45R11 compounds(R¼La, Ce, Pr, Nd, Sm, Gd, U), J. Less-Common Met., 1979, 64, 221–231.
R. E. Rundle and A. S. Wilson, The structures of some metal compounds of U,Acta Crystallogr., 1949, 2, 148–150.
Y–Hg
Phase Crystal structure Lattice parameters (nm) Density (g cm–3) Prototype
YHg Cubic a¼ 0.3677 CsClYHg2 Trigonal a¼ 0.4779, c¼ 0.3471 CeCd2YHg3 Hexagonal a¼ 0.6528, c¼ 0.486 Ni3SnY11Hg45 Cubic Sm11Cd45
H. R. Kirchmayr, Compounds of Y, Sm and Gd with Hg, Acta Phys.Austriaca, 1964, 18, 193–204.
E. Laube and H. Nowotny, Die Kristallstrukturen von ScHg, ScHg3, YCd,YHg und YHg3, Monatsh. Chem., 1963, 94, 851–858.
Yb–Hg
Phase Crystal structure Lattice parameters (nm) Density (g cm–3) Prototype
Yb2HgYbHg Cubic a¼ 0.3731 CsClYbHg2 Trigonal a¼ 0.4896, c¼ 0.3534 CeCd2YbHg3 Hexagonal a¼ 0.6596, c¼ 0.5021 Ni3SnYb14Hg51 Cubic a¼ 1.341, b¼ 0.961 Gd14Ag51
A. Iandelli and A. Palenzona, Atomic size of rare earths in intermetalliccompounds, MX compounds of CsCl type, J. Less-Common Met., 1965, 9,1–6.
A. Iandelli and A. Palenzona, Crystal chemistry of intermetallic compounds, inHandbook on the Physics and Chemistry of Rare Earths, ed. K. A. GschneidnerJr and L Eyring, North-Holland, Amsterdam, 1979, pp. 1–54.
H. R. Kirchmayr and W. Lugscheider, Structure of Tb–Hg and Yb–Hgsystems, Z. Metallkd., 1968, 59, 296–297.
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F. Lihl, Phase Diagrams of Yb–Hg and Tb–Hg, US Government ReportAD-658216, 1967.
F. Merlo and M. L. Fornasini, Crystal structure of the R11Hg45 compounds(R¼La, Ce, Pr, Nd, Sm, Gd, Yb, U), J. Less-Common Met., 1979, 64,221–231.
A. Palenzona, MX3 intermetallic phase of the rare earths with Hg, In, Tl, Pb,J. Less-Common Met., 1966, 10, 290–292.
Zn–Hg
PhaseCrystalstructure
Lattice parameters(nm)
Density(g cm–3) Prototype
g-(Zn3Hg) 70–77% Zn Orthorhombic a¼ 0.2708, b¼ 0.4696,c¼ 0.5471
b0-Cu3Ti
b-(Zn2Hg or Zn3Hg2)56–67% Zn
ZnHg3 Hexagonal
E. Cohen and P. J. H. van Ginneken, Die Zinkamalgame und der ClarkischeNormalelement, Z. Phys. Chem., 1911, 75, 437–493.
R. Kubiak, M. Wolcyrz and W. Zacharko, New phase in the Hg–Zn system:Hg3Zn, Cryst. Res. Technol., 1988, 23, K57–K59.
M. Puselj, Z. Ban and A. Drasner, On the crystal structure of HgZn3,Z. Naturforsch., 1982, 37B, 557–559.
Zr–Hg
Phase Crystal structure Lattice parameters (nm) Density (g cm–3) Prototype
ZrHg Tetragonal a¼ 0.315, c¼ 0.417 AuCuZr3Hg Cubic a¼ 0.55583 b-WZrHg3 Cubic a¼ 0.43652 AuCu
E. E. Havinga, H. Damsma and M. H. Van Maaren, Oscillatory dependence ofsuperconductive critical temperature on number of valency electrons inCu3Au-type alloys, J. Phys. Chem. Solids, 1970, 31, 2653–2662.
P. Pietrokowsky, A cursory investigation of intermediate phases in the systemsTi–Zn, Ti–Hg, Zr–Zn, Zr–Cd and Zr–Hg by X-ray powder diffractionmethod, J. Met., 1954, 6, 219–226.
E. Vielhaber and H.-L. Luo, New A-15 phases, Solid State Commun., 1967, 5,321–323.
Phase Diagrams and Intermetallic Compounds in Binary Amalgam Systems 271
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APPENDIX II
Density and Surface Tension ofBinary Amalgams
Bi–Hg
xBi (mole fraction) T (K) Density (g cm–3) s (mNm–1) Ref.
0.10 373 12.98 409 1393 12.94 429 1424 12.88 444 1497 12.73 437 1567 12.59 421 1638 12.45 402 1
0.19 370 12.63 419 1478 12.44 428 1557 12.30 422 1628 12.17 410 1
0.34 420 12.01 412 1487 11.91 415 1511 11.87 416 1557 11.80 411 1628 11.69 404 1
0.47 438 11.54 380 1448 11.53 390 1477 11.48 405 1518 11.42 404 1557 11.36 400 1626 11.27 396 1671 11.20 392 1
0.70 490 10.81 386 1515 10.77 390 1575 10.69 386 1636 10.61 382 1668 10.57 379 1
0.83 533 10.40 382 1571 10.36 380 1618 10.30 377 1673 10.23 373 1
Mercury Handbook: Chemistry, Applications and Environmental Impact
By Leonid F Kozin and Steve Hansen
r L F Kozin and S C Hansen 2013
Published by the Royal Society of Chemistry, www.rsc.org
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1. Kh. I. Ibragimov and V. S. Savvin, Surface tension of the Hg–M (M¼Cd,In, Sn, Tl, Pb, Bi) amalgams, Inorg. Mater., 1996, 32, 963–970.
Cd–Hg
xCd (mole fraction) T (K) Density (g cm–3) s (mNm–1) Ref.
0.26 373 12.37 507 1423 12.26 497 1473 12.15 486 1523 12.04 474 1573 11.93 462 1
0.52 430 11.03 527 1480 10.94 560 1520 10.86 556 1578 10.76 545 1678 10.57 527 1
0.74 519 9.623 574 10.74 553 9.570 587 1
580 9.527 587 1615 9.473 599 1659 9.404 586 1
0.85 506 9.055 538 1578 8.951 595 1622 8.888 601 1691 8.789 597 1
1. Kh. I. Ibragimov and V. S. Savvin, Surface tension of the Hg–M (M¼Cd,In, Sn, Tl, Pb, Bi) amalgams, Inorg. Mater., 1996, 32, 963.
Cs-Hg
xCs (mole fraction) T (K) s (mN m–1) Ref.
0 295 462.0 20.000080 295 385.8 20.000160 295 378.4 20.000241 295 375.3 20.000421 295 372.1 20.000562 295 369.0 20.000722 295 366.4 20.000903 295 354.2 20.00112 295 363.4 20.00136 295 362.0 20.00162 295 360.4 20.00197 295 359.1 20.00233 295 357.2 20.00317 295 356.0 20.00357 295 353.8 20.00403 295 353.0 20.00457 295 351.7 20.00520 295 350.7 20.00598 295 349.7 2
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xCs (mole fraction) T (K) s (mN m–1) Ref.
0.00678 295 348.6 20.00776 295 347.6 20.00885 295 346.5 20.01000 295 345.0 2
1. V. B. Lazarev, Y. I. Malov and G. A. Sharpataya, Work function andsurface tension of concentrated cesium amalgams, Dokl. Akad. Nauk SSSR,1968, 178, 355.
2. P. P. Pugachevich and O. A. Timofeevicheva, Experimental study of thesurface tension of metallic solutions. II. Surface tension of very dilutealkali-metal amalgams at 221, Russ. J. Phys. Chem., 1959, 33, 350.
In–Hg
xIn (mole fraction) T (K) Density (g cm–3) s (mNm–1) Ref.
0 293 483 10.076 293 489 10.126 293 500 10.140 293 488 10.146 293 500 10.207 293 500 10.294 293 520 10.429 293 534 10.642 293 555 10.756 294 556 10 298 13.534 485.1 40.163 298 12.533 495.9 40.368 298 11.224 529.9 40.636 298 9.470 563.3 40 373 471 10.074 373 479 10.123 373 487 10.140 373 477 10.143 373 486 10.207 373 485 10.236 374 487 10.294 373 509 10.428 373 507 10.429 373 524 10.569 373 525 10.641 373 546 10.756 373 547 10 433 460 10.075 433 469 10.122 433 475 10.140 433 466 10.147 433 478 10.236 433 477 10.297 433 500 10.428 433 499 1
274 Appendix II
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xIn (mole fraction) T (K) Density (g cm–3) s (mNm–1) Ref.
0.428 433 515 10.569 432 514 10.644 433 534 10.756 433 533 10.878 433 556 10 503 412 20.038 503 416 20.073 503 424 20.206 503 459 20.285 503 484 20.424 503 511 20.481 503 512 20.528 503 516 20.617 503 519 20.715 503 524 20.835 503 531 20.900 503 535 20.954 503 545 20.977 503 550 21.000 503 551 2
1. Y. Oguchi, T. Itami and M. Shimoji, Surface tension of liquid In–Hgamalgams, Phys. Chem. Liq., 1981, 10, 315.
2. Kh. I. Ibragimov, Interpretation of the surface tension of mercury inamalgam systems within the framework of the Mott theory, Russ. J. Phys.Chem., 1980, 54, 90.
3. Kh. I. Ibragimov and S. L. Aziev, The surface properties of indium–mercurymelts, Russ. J. Phys. Chem., 1976, 50, 168 (VINITI Document No. 2874-75,deposited 9 October 1975).
4. D. A. Olsen and D. C. Johnson, The surface tension of mercury–thalliumand mercury–indium amalgams, J. Phys. Chem., 1963, 67, 2529.
K–Hg
xK (mole fraction) T (K) s (mNm–1) Ref.
0 295 462.0 10.00000249 295 426.0 10.00000722 295 420.3 10.0000194 295 414.0 10.0000550 295 406.9 10.000123 295 401.4 10.000236 295 396.3 10.000399 295 393.0 10.000594 295 389.8 10.000847 295 386.8 10.001242 295 383.9 10.001766 295 381.1 10.002368 295 378.6 10.002708 295 378.5 1
Density and Surface Tension of Binary Amalgams 275
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xK (mole fraction) T (K) s (mNm–1) Ref.
0 293 467 20.00025 293 404 20.0012 293 384 20.0021 293 390 20.0027 293 388 20.0035 293 385 20.0040 293 382 20.0050 293 380 20.0065 293 377 2
1. P. P. Pugachevich and O. A. Timofeevicheva, Experimental study of thesurface tension of metallic solutions. II. Surface tension of very dilutealkali-metal amalgams at 221, Russ. J. Phys. Chem., 1959, 33, 350.
2. P. P. Pugachevich, Experimental study of surface tension of potassiumamalgam, Dokl. Akad. Nauk SSSR, 1951, 74, 831.
Na–Hg
xNa (mole fraction) T (K) s (mN m–1) Ref.
0 295 463.1 20.00000080 295 460.4 20.00000421 295 459.2 20.00000843 295 458.5 20.0000106 295 457.8 20.0000148 295 456.9 20.0000184 295 456.3 20.0000231 295 455.7 20.0000273 295 454.4 20.0000313 295 454.0 20.0000353 295 452.6 20.0000405 295 452.5 20.0000485 295 450.2 20.0000568 295 448.2 20.0000682 295 445.3 20.0000802 295 444.3 20.0000931 295 442.6 20.000105 295 441.4 20.000117 295 440.5 20.000129 295 439.7 20.000148 295 439.0 20.000164 295 438.0 20.000183 295 437.4 20.000201 295 436.5 20.0002 298–623K (20–350 1C) 454–0.260(T, 1C) 4
1. A. Y. Lee, Effect of sodium concentration on the surface tension of mercury,Ind. Eng. Chem. Prod. Res. Dev., 1968, 7, 66.
276 Appendix II
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2. P. P. Pugachevich and O. A. Timofeevicheva, Experimental study of thesurface tension of metallic solutions. II. Surface tension of very dilutealkali-metal amalgams at 221, Russ. J. Phys. Chem., 1959, 33, 350.
3. P. P. Pugachevich and O. A. Timofeevicheva, Dokl. Akad. Nauk SSSR,1954, 94, 285.
4. A. I. Pridantsev, L. A. Gavrilov, L. S. Kokorev, A. A. Smirnov and V. I.Petrovichev, Adhesion and surface tension of mercury and amalgams ofsodium and magnesium, Voprosy Teplofiziki Yadernykh Reaktorov, 1969,(2), 41–48.
Pb–Hg
xPb (mole fraction) T (K) Density (g cm–3) s (mNm–1) Ref.
0.29 423 12.59 470 10.40 423 12.34 478 10.53 523 11.89 471 10.58 523 11.79 472 10.67 523 11.61 469 10.53 573 11.82 463 10.58 573 11.72 466 10.67 573 11.54 463 10.78 573 11.30 460 10 623 383 20.095 623 402 20.196 623 410 20.293 623 427 20.403 623 442 20.500 623 452 20.532 623 453 20.583 623 456 20.651 623 454 20.677 623 457 20.783 623 453 20.912 623 451 21.0 623 443 20.53 673 11.67 449 10.58 673 11.58 454 10.67 673 11.41 455 10.78 673 11.17 451 10.91 673 10.87 446 1
Pb–Hg (continued)
xPb (mole fraction)
s¼s0 – aT (mN m–1)3 r¼ r0 – bT (g cm–3)4
s0 a r0 b
0 487 0.281 13.53 0.00240.041 487 0.247 13.52 0.00240.096 490 0.226 13.44 0.00230.234 502 0.203 13.15 0.00210.352 513 0.183 12.94 0.00200.389 514 0.173 12.83 0.0019
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xPb (mole fraction)
s¼s0 – aT (mN m–1)3 r¼ r0 – bT (g cm–3)4
s0 a r0 b
0.441 513 0.154 12.71 0.00190.528 513 0.147 12.47 0.00180.577 509 0.139 12.33 0.00170.649 501 0.121 12.13 0.00170.665 496 0.106 12.05 0.00160.780 484 0.089 11.69 0.00150.787 479 0.072 11.68 0.00150.911 481 0.098 11.28 0.00131.000 469 0.086 11.05 0.0013
1. Kh. I. Ibragimov and V. S. Savvin, Surface tension of the Hg–M (M¼Cd,In, Sn, Tl, Pb, Bi) amalgams, Inorg. Mater., 1996, 32, 963.
2. Kh. I. Ibragimov, Interpretation of the surface tension of mercury inamalgam systems within the framework of the Mott theory, Russ. J. Phys.Chem., 1980, 54, 90.
3. Kh. I. Ibragimov and V. S. Savvin, Surface tension and density of Hg–Pbmelts, Izv. Vyssh. Uchebn. Zaved. Tsvet. Metall., 1976, (4), 148–149.
4. M. P. Vukalovich, A. I. Ivanov, et al., Thermophysical Properties ofMercury, Standards Publishing House, Moscow, 1971.
Rb–Hg1
xRb (mole fraction) T (K) s (mNm–1)
0 298 4750.0000048 298 405.10.0000068 298 401.00.000049 298 383.20.00015 298 374.50.00045 298 370.20.00061 298 369.20.00180 298 364.00.00670 298 355.5
1. Yu. I. Malov, Kh. I. Badakhov and V. B. Lazarev, Elektrokhimiya, 1971, 7,432 (translation: Work function and surface tension in dilute rubidiumamalgams, Sov. Electrochem., 1971, 7, 416).
Sn–Hg
xSn (mole fraction) T (K) s (mNm–1) Ref.
0.051 523 539 10.097 523 537 10.151 523 533 1
278 Appendix II
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xSn (mole fraction) T (K) s (mNm–1) Ref.
0.218 523 528 10.280 523 519 10.344 523 515 10.414 523 504 10.516 523 488 10.621 523 471 10.710 523 454 10.785 523 444 10.823 523 439 10.850 523 434 10.893 523 428 10.941 523 424 10.027 597 391.4 20.055 597 394.4 20.107 597 399.2 20.150 597 407.3 20.177 597 412.5 20.217 597 419.5 20.286 597 431.7 20.378 597 452.0 20.473 597 473.4 20.576 597 491.8 20.650 597 503.2 20.702 597 511.0 20.769 597 520.2 20.831 597 527.6 20.878 597 531.7 20.925 597 534.6 20.962 597 536.5 20.048 623 533 10.097 623 531 10.151 623 527 10.218 623 522 10.280 623 512 10.341 623 505 10.414 623 494 10.516 623 475 10.618 623 456 10.780 623 436 10.782 623 423 10.820 623 417 10.847 623 411 10.893 623 405 10.944 623 398 1
1. Kh. I. Ibragimov and V. S. Savvin, Surface tension of the Hg–M (M¼Cd,In, Sn, Tl, Pb, Bi) amalgams, Inorg. Mater., 1996, 32, 963.
2. Kh. I. Ibragimov, Interpretation of the surface tension of mercury inamalgam systems within the framework of the Mott theory, Russ. J. Phys.Chem., 1980, 54, 90.
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Tl-Hg
xTl (mole fraction) T (K) Density (g cm–3) s (mNm–1) Ref.
0.10 299 13.27 468 1329 13.20 464 1373 13.10 458 1471 12.89 439 1587 12.63 411 1680 12.42 386 1
0.31 303 12.77 471 1360 12.66 467 1396 12.60 464 1493 12.42 452 1580 12.26 437 1673 12.09 420 1729 11.99 408 1
0.47 373 12.35 472 1418 12.27 467 1523 12.08 455 1613 11.92 443 1723 11.73 426 1
0.69 488 11.78 464 1548 11.67 458 1599 11.59 452 1683 11.45 441 1723 11.38 435 1
0 298 13.534 485.1 50.0196 298 13.490 477.4 50.0393 298 13.443 474.3 50.0590 298 13.405 472.5 50.0836 298 13.353 471.0 50.1082 298 13.305 473.0 50.1279 298 13.258 475.0 50.1476 298 13.222 478.1 50.2465 298 13.021 479.0 50.3955 298 12.727 480.9 50.020 573 401 20.048 573 403 20.066 573 406 20.082 573 407 20.101 573 410 20.132 573 415 20.308 573 434 20.468 573 445 20.685 573 454 20.997 573 462 2
1. Kh. I. Ibragimov and V. S. Savvin, Surface tension of the Hg–M (M¼Cd,In, Sn, Tl, Pb, Bi) amalgams, Inorg. Mater., 1996, 32, 963.
2. Kh. I. Ibragimov, Interpretation of the surface tension of mercury inamalgam systems within the framework of the Mott theory, Russ. J. Phys.Chem., 1980, 54, 90.
3. Kh. I. Ibragimov and V.S. Savvin, The surface tension of melts in the thallium–mercury system, Fiz.-Khim. Issled. Metall. Protsessov, 1980, (8), 61–66.
280 Appendix II
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4. S. L. Aziev and Kh. I. Ibragimov, Surface tension and density of thethallium–mercury system, Russ. J. Phys. Chem., 1975, 49, 952 (VINITIDocument No. 621-75, deposited 10 March 1975).
5. D. A. Olsen and D. C. Johnson, The surface tension of mercury–thalliumand mercury–indium amalgams, J. Phys. Chem., 1963, 67, 2529.
Zn–Hg
xZn (mole fraction)
s (mNm–1)
298K 323K 373K 423K 473K 523K 573K 623K
0 465 462 452 439 429 416 402 3870.009 470 467 457 446 434 421 407 3920.017 471 468 459 447 436 423 409 3930.030 475 470 461 448 438 424 411 3950.058 477 474 464 454 442 432 419 4020.113 467 458 448 438 426 4120.167 474 463 455 446 436 4220.226 468 463 452 446 4350.304 479 474 470 462 4540.384 488 487 483 4770.467 519 515 5100.530 544 540 5380.574 556 5520.643 584 5820.679 598 5960.765 6350.825 670
xZn (mole fraction)
Density (g cm–3)
298K 323K 373K 423K 473K 523K 573K 623K
0.009 13.464 13.409 13.294 13.180 13.065 12.950 12.835 12.7200.017 13.435 13.380 13.265 13.150 13.035 12.920 12.805 12.6900.030 13.415 13.360 13.245 13.130 13.015 12.900 12.784 12.6700.058 13.254 13.205 13.105 12.974 12.890 12.775 12.675 12.5690.113 12.840 12.737 12.640 12.538 12.450 12.3400.167 12.590 12.512 12.420 12.390 12.295 12.1900.226 12.360 12.250 12.150 12.050 11.9600.304 12.125 12.020 11.915 11.810 11.7050.384 11.585 11.492 11.404 11.3220.467 11.007 10.931 10.8500.530 10.657 10.583 10.5090.574 10.329 10.2500.643 9.887 9.8040.679 9.674 9.5940.765 8.9700.825 8.420
1. Kh. I. Ibragimov, A. G.-M. Nal’giev and B. B. Sagov, The surfaceproperties of liquid mercury–zinc alloys, Russ. J. Phys. Chem., 1975, 49,1097 (VINITI Document No. 1014-75, deposited 10 April 1975).
Density and Surface Tension of Binary Amalgams 281
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APPENDIX III
Inorganic and Organic MercuryCompounds
Tables of inorganic and organic mercury compounds hare been assembled.Crystal structure determination was used as the criterion for selectingcompounds because it prevents the possibility of incorrectly assigning chemicalformulae.
Amido Compounds
Name Formula MW Color Crystal structure Ref.
Mercury(II) amidochloride HgNH2Cl 252.066 Orthorhombic 1Mercury(II) amidobromide HgNH2Br 296.517 Orthorhombic 2Iminomercury(II) bromide Hg2NHBr2 576.003 Hexagonal 3Mercury(I) nitrite Hg2(NO2)2 493.190 Monoclinic 4
1. W. N. Lipscomb, Acta Crystallogr., 1951, 4, 266.2. L. Nijssen and W. N. Lipscomb, Acta Crystallogr., 1952, 5, 604.3. K. Brodersen, Acta Crystallogr., 1955, 8, 723.4. S. Ohba, F. Matsumoto, M. Ishihara and Y. Saito, Acta Crystallogr., 1986,
C42, 1.
Arsenides and Arsenates
Name Formula MW Color Crystal structure Ref.
Mercury(I)orthoarsenate
a-(Hg2)3(AsO4)2 1481.376 Red–brown Monoclinic 1
Mercury(I)orthoarsenate
b-(Hg2)3(AsO4)2 1481.376
Mercury(I)diarsenate(V)
(Hg2)2(As2O7) 1064.197 Orthorhombic 2[Hg3](PO4)Cl 732.193 3
Mercury Handbook: Chemistry, Applications and Environmental Impact
By Leonid F Kozin and Steve Hansen
r L F Kozin and S C Hansen 2013
Published by the Royal Society of Chemistry, www.rsc.org
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Name Formula MW Color Crystal structure Ref.
[Hg3](AsO4)Br 820.592 3[Hg3](AsO4)Cl 776.141 3
Mercury(II)arsenate
Hg3(AsO4)2 879.606 Monoclinic 4(Hg3)3(AsO4)4 2360.982 5, 6(Hg)3[HgO2]Cl2 905.264 7
1. B. Kamenar and B. Kaitner, Acta Crystallogr., 1973, B29, 1666.2. M. Weil, Z. Anorg. Allg. Chem., 2004, 630, 213.3. M. Weil, Z. Naturforsch., 2001, 56B, 753.4. A.-K. Larsson, S. Lidin, C. Stalhandske and J. Albertsson, Acta Cryst-
allogr., 1993, C49, 784.5. M. Weil and R. Glaum, J. Solid State Chem., 2001, 157, 68.6. A. L. Wessels, W. Jeitschko and M. H. Moller, 1997, Z. Naturforsch., 52B,
469.7. S. V. Borisov, S. A. Magarill and N. V. Pervukhina, J. Struct. Chem., 2003,
44, 441.
Antimonides
Name Formula MW Color Crystal structure Ref.
Mercury antimonyoxide
Hg2Sb2O7 957.292 Cubic 1
1. V. I. Sidey, P. M. Milyan, O. O. Semrad and A. M. Solomon, J. AlloysCompd., 2008, 457, 480.
Azides
Name Formula MW Color Crystal structure Ref.
Mercury(I) azide Hg2(N3)2 485.220 White Monoclinic 1Synonym:diazidodimercury
Light-sensitive
Mercury(II) azide a-Hg(N3)2 284.630 Orthorhombic 2b-Hg(N3)2 284.630 2
1. P. Nockemann, U. Cremer, U. Ruschewitz and G. Meyer, Z. Anorg. Allg.Chem., 2003, 629, 2079.
2. U. Muller, Z. Anorg. Allg. Chem., 1973, 399, 183.
Borates
Name Formula MW Color Crystal structure Ref.
a-HgB4O7 355.827 1b-HgB4O7 355.827 Orthorhombic 2 (high-pressure phase)
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1. M. Weil, Acta Crystallogr., 2003, E59, i40.2. H. Emmea, M. Weil and H. Huppertz, Z. Naturforsch., 2005, 60B, 815.
Bromides and Bromates
Name Formula MW ColorCrystalstructure Ref.
Mercury(I)bromide
Hg2Br2 560.988 Ferroelectricphase formsat 143 K
SeeChapter 51, 2
Mercury(II)bromide
HgBr2 360.398 SeeChapter 5
Mercury(II)iminobromide
Hg2(NH)Br2 576.003 Hexagonal 3
Millon’s base Hg2NBr 495.091 Tridymite Hexagonal 4Hg2NOH �2H2O
451.221 Cristobalite Cubic 5
Mercury(I)bromate
Hg2(BrO3)2 656.984 Colorless Monoclinic 6
Mercury(II)hydroxybromate(mercurybromatehydroxide)
Hg(OH)BrO3 345.499 7, 8
Mercury(I,II)bromide oxide
Hg8O4Br3 1908.446 Monoclinic 9
1. E. Dorm, J. Chem. Soc. D, 1971, 466–467.2. M. E. Boiko, B. S. Zadokhin and K. Lukaszewicz, Fiz. Tverd. Tela
(Leningrad), 1993, 35, 1483.3. K. Brodersen, Acta Crystallogr., 1955, 8, 723.4. L. Nijssen and W. N. Lipscomb, Acta Crystallogr., 1954, 7, 103.5. W. N. Lipscomb, Acta Crystallogr., 1951, 4, 156.6. E. Dorm, et al., Acta Chem. Scand., 1967, 21, 1661.7. A. Weiss, et al., Z. Naturforsch., 1960, 15B, 678.8. G. Bjornlund, Acta Chem. Scand., 1971, 25, 1645.9. C. Stalhandske, Acta Chem. Scand., 1987, A41, 576.
Cyanimides and Carbonates
Name Formula MW ColorCrystalstructure Ref.
Mercury cyanamide HgNCN(II) 240.615 1Mercury carbodiimide HgNCN(I) 240.615 2, 3Mercury(I) carbonate Hg2CO3 461.189 White Monoclinic 4
1. X. Liu, P. Muller, P. Kroll and R. Dronskowski, Inorg. Chem., 2002, 41,4259.
2. S. K. Deb and A. D. Yoffe, Trans. Faraday Soc., 1958, 55, 106.
284 Appendix III
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3. M. Becker and M. Jansen, Z. Anorg. Allg. Chem., 2000, 626, 1639.4. A. N. Christensen, P. Norby and J. C. Hanson, Z. Kristallogr., 1994, 209,
874.
Chlorides and Chlorates
Name Formula MW. ColorCrystalstructure Ref.
Mercury(I)chloride
a-Hg2Cl2 472.088 Tetragonal 1, 2
b-Hg2Cl2 472.088 2Mercury(II)chloride
HgCl2 271.498 White,light-sensitive
Tetragonal SeeChapter 5
Cesium mercurytetrachloride
Cs2HgCl4 608.212 Orthorhombic 32HgCl2 �HgO(Hg3Cl3)OCl
Cubic 4
Mercury chlorideoxide
a-HgCl2 � 2HgOa-Hg3Cl2O2
704.674 Black Monoclinic 5–7
Mercury chlorideoxide
b-Hg3Cl2O2 704.674 Dark red Monoclinic 7–9Hg(OH)ClO3 301.047 10HgCl2 � 4HgO 1268.060 Brown
BlackOrthorhombic 11
Mercury(I)chlorate
Hg2(ClO3)2 568.08 Monoclinic 12
Mercuryoxychloride
Hg3OCl 653.222 Monoclinic 13
Mercury(II)chlorate
Hg(ClO3)2 367.492 White 14
Mercury chlorideoxide
Hg4O2Cl2 905.264 Lightyellow
Monoclinic 15–17
Mercury(II)hydroxidechlorate(V)
Hg(OH)ClO3 301.047 Orthorhombic 10[Hg2]3O2Cl2 1306.444 Monoclinic 7Hg5O4Cl2 1137.852 Orthorhombic 7[Hg2]3HgO3Cl2 1523.033 Orthorhombic 7Hg8O4Br3 1908.446 Monoclinic 7
1. N. J. Calos, C. H. L. Kennard and R. L. Davis, Z. Kristallogr., 1989, 187,305.
2. C. Guminski, J. Phase Equilib., 1994, 15, 101.3. B. Bagautdinov, J. Luedecke, M. Schneider and S. van Smaalen, Acta
Crystallogr., 1998, B54, 6264. D. Grdenic and S. Scavnicar, Nature, 1953, 172, 584.5. S. Scavnicar, Acta Crystallogr., 1955, 8, 379.6. K. Aurivillius, et al., Acta Crystallogr., 1974, B30, 1907.7. S. V. Borisov, S. A. Magarill and N. V. Pervukhina, J. Struct. Chem., 2003,
44, 1018.8. K. Aurivillius, et al., Acta Crystallogr., 1978, B34, 79.9. M.A. Neuman, et al., J. Cryst. Mol. Struct., 1976, 6, 177.
Inorganic and Organic Mercury Compounds 285
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10. D. Gobbels and M.S. Wickleder, Acta Crystallogr., 2004, E60, i40.11. A. Weiss, G. Nagorsen and A. Weiss, Z. Kristallogr., 1954, 9B, 81.12. D. Gobbels and G. Meyer, Z. Anorg. Allg. Chem., 2003, 629, 2446.13. N. V. Pervukhina, G. V. Romanenko, S. A. Magarill, V. I. Vasiliev and S.
V. Borisov, J. Struct. Chem., 1999, 40, 155.14. J. Lamure, et al., in Nouveau Traite de Chimie Minerale, ed. P. Pascal,
Masson, Paris, 1962, vol. 5, p. 739.15. K. Aurivilius and L. Folkmarsson, Acta Chem. Scand., 1968, 22,
2529.16. S. Scavnicar, Acta Crystallogr., 1956, 9, 956.17. K. Broderson, G. Gobel and G. Liehr, Z. Anorg. Allg. Chem., 1989, 575,
145.
Chromates
Name Formula MW ColorCrystalstructure Ref.
Mercury(I) chromate a-Hg2CrO4 517.172 1Mercury(I) chromate b-Hg2CrO4 517.172 1Mercury(II) chromate a-HgCrO4 316.584 Monoclinic 2–4Mercury(II) chromate b-HgCrO4 316.584 Orthorhombic 2
HgCrO4 �H2O 334.597 Triclinic 2Mercury(II) chromatehemihydrate
HgCrO4 � 12H2O 325.590 Monoclinic 5, 6
Mercury chromateoxide
Hg3(CrO4)O2
HgCrO4 � 2HgO749.762 4, 7, 8
Hg6Cr2O9 1451.523 Orange Orthorhombic 9Hg6Cr2O10 1467.522 Red Orthorhombic 9
Mercury(II) dichromate HgCr2O7 416.575 Tetragonal 10HgCr2O4 368.578 Cubic 11HgCr2O4 368.578 12
1. M. Weil and B. Stoger, Z. Anorg. Allg. Chem., 2006, 632, 2131.2. B. Stoger and M. Weil, Z. Naturforsch., 2006, 61B 708.3. C. Stalhandske, Acta Crystallogr., 1978, B34, 1968.4. K. Aurivillius, et al., Acta Chem. Scand., 1961, 15, 1932.5. K. Aurivillius and C. Stalhandske, Z. Kristallogr., 1975, 142, 129.6. K. Aurivillius, Acta Chem. Scand., 1972, 26, 2113.7. G. Nogorsen, et al., Angew. Chem. Int. Ed. Engl., 1962, 1, 115.8. J. Lamure, C. R. Hebd. Seances Acad. Sci., 1963, 256, 3696.9. M. Weil and B. Stoger, J. Solid State Chem., 2006, 179, 2479.
10. M. Weil, B. Stoger, E. Zobetz and E. J. Baran, Monatsh. Chem., 2006, 137,987.
11. A.L. Wessels, R. Czekalla and W. Jeitschko, Mater. Res. Bull., 1998,33, 95.
12. M. Weil and B. Stoger, Acta Crystallogr., 2006, E62, i199.
286 Appendix III
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Cyanides and Cyanates
Name Formula MW ColorCrystalstructure Ref.
Mercury(II) cyanide Hg(CN)2 252.626 Monoclinic 1Mercury(II) cyanide Hg(CN)2 252.626 Orthorhombic 1Mercury(II) cyanide Hg(CN)2 252.625 Four high-
pressurephases
2–4
Mercury cyanamide HgCN2 240.615 Orthorhombic 5HgNCN(I) 240.615 5, 6HgNCN(II) 240.615 Monoclinic 7Hg2(CN2)Cl2 512.114 8Hg3(CN2)2Cl2 752.73 8
Potassiumtetracyanomercurate
a-K2[Hg(CN)4] 382.858 Trigonal 9, 10
Potassiumtetracyanomercurate
b-K2[Hg(CN)4] 382.858 Cubic 9, 10
Rubidiumtetracyanomercurate
a-Rb2Hg(CN)4 475.598 9, 11
Rubidiumtetracyanomercurate
b-Rb2Hg(CN)4 475.598 9, 11
Mercuric oxycyanide HgO �Hg(CN)2 469.218 Orthorhombic 12Mercury(II)oxycyanide
HgO �Hg(CN)2 469.218 WhiteExplosive,sensitiveto impactand heat
Orthorhombic 12
Mercury(II)cyanonitrate
Hg(CN)NO3 288.613 Hexagonal 13
Mercury fulminate Hg(CNO)2 284.624 Orthorhombic 14
1. R. C. Seccombe and C. H. L. Kennard, J. Organomet. Chem., 1969, 18,243.
2. J. Hvoslef, Acta Chem. Scand., 1958, 12, 1568.3. D. M. Adams, et al., J. Phys. C: Solid State Phys., 1983, 16, 3349.4. P. T. T. Wong, J. Chem. Phys., 1984, 80, 5937.5. M. Becker and M. Jansen, Z. Anorg. Allg. Chem., 2000, 626 1639.6. X. Liu, Dissertation, Aachen University of Technology (RWTH),
2002.7. X. Liu, P. Muller, P. Kroll and R. Dronskowski, Inorg. Chem., 2002, 41,
4259.8. X. Liu and R. Dronskowski, Z. Naturforsch., 2002, 57B, 1108.9. L. Wiehl and S. Haussuhl, Z. Kristallogr., 1981, 156, 117.
10. T. Asaji and R. Ikeda, J. Mol. Struct., 1995, 345, 93.11. P. Klufers, H. Fuess and S. Haussuhl, Z. Kristallogr., 1981, 156, 255.12. S. Scavnicar, Z. Kristallogr., 1963, 118, 248.13. C. Mahon and D. Britton, Inorg. Chem., 1971, 10, 2331.14. W. Beck, J. Evers, M. Gobel, G. Oehlinger and T. M. Klapotke, Z. Anorg.
Allg. Chem., 2007, 633, 1417.
Inorganic and Organic Mercury Compounds 287
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Fluorides
Name Formula MW Color Crystal structure Ref.
Hg2F2 439.176 See Chapter 5Hg(OH)F 236.597 Orthorhombic 1, 2Hg2PO3F 499.149 3HgF2 238.586 See Chapter 5HgF4 276.582 4
Mercuryhexafluoroniobate
Hg3NbF6 808.664 5
Mercuryhexafluorotantalate
Hg3TaF6 896.706 5
1. D. Grdenic and M. Sikirica, Inorg. Chem., 1973, 12, 544.2. C. Stalhandske, Acta Crystallogr., 1979, B35, 949.3. M. Weil, M. Puchberger and E. J. Baran, Inorg. Chem., 2004, 43,
8330.4. X. Wang, L. Andrews, S. Riedel and M. Kaupp, Angew. Chem. Int. Ed.,
2007, 46, 8371.5. I. D. Brown, R. J. Gillespie and K. R. Morgan, Inorg. Chem., 1984, 23,
4506.
Iodides and Iodates
Name Formula MW ColorCrystalstructure Ref.
Mercury(I) iodide Hg2I2 654.988 See 5.2.7Mercury(II) iodide a-HgI2 454.398
b-HgI2 454.398 See 5.2.8Mercury arsenideiodide
Hg4As2I3 1332.917 Black 1, 2
Mercury phosphidehexaiodide
Hg9P5I6 2721.604 Monoclinic 3
Mercury(I,II) oxideiodide
Hg2OI 544.083 Monoclinic 4, 5
Mercury(II) iodate a-Hg(IO3)2 550.392 6b-Hg(IO3)2 550.392 Monoclinic 6Hg(H3IO6) 426.512 7Hg3(H2IO6)2 1051.598 7
1. H. Puff, et al., Z. Anorg. Allg. Chem., 1965, 341, 217.2. P. L. Labbe, et al., Z. Kristallogr., 1989, 187, 117.3. M. Ledesert, A. Rebbah and P. Labbe, Z. Kristallogr., 1990, 192, 223.4. C. Stalhandske, K. Aurivillius and G.-I. Bertinsson, Acta Crystallogr., 1985,
C41, 167.5. S. V. Borisov, S. A. Magarill and N. V. Pervukhina, J. Struct. Chem., 2003,
44, 1018.6. M. Weil, Z. Naturforsch., 2003, 58B, 627.7. T. J. Mormann and W. Jeitschko, Z. Kristallogr., 2001, 216, 1.
288 Appendix III
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Iodomercurates
Name Formula MW Color Crystal structure Ref.
Sodium iodomercurate Na2HgI4 754.186Potassiumiodomercurate
K2HgI4 786.402
Cadmiumiodomercurate
Cd2HgI4 933.028 1
Lead iodomercurate Pb2HgI4 1122.606 1Silver iodomercurate a-Ag2HgI4 923.942 2
b-Ag2HgI4 923.942 3d-Ag2HgI4 923.942 4e-Ag2HgI4 923.942 4
Copper iodomercurate a-Cu2HgI4 835.298 2, 5b-Cu2HgI4 835.298d-Cu2HgI4 835.298 4
Hexagonal – highpressure
6
Cesium iodomercurate Cs2HgI4 974.016 Monoclinic 7Cs3HgI5 1233.830 Orthorhombic 7Cs2Hg3I8 �H2O 1900.827 Monoclinic 7
Sulfur iodomercurate Hg3S2I2 Orange Orthorhombic 8Selenium iodomercurate Hg3Se2I2 Light
redOrthorhombic 8
Telluriumiodomercurate
Hg3TeI4 Cubic 9
Thallium iodomercurate Tl4HgI6 1779.546 Yellow 10
1. J. A. A. Ketelaar, Z. Phys., Chem., 1934, B26, 327.2. S. Hull and D. A. Keen, J. Phys.: Condens. Matter, 2000, 12, 3751.3. K. W. Browall, J. S. Kasper and H. Wiedemeier, J. Solid State Chem.,
1974, 10, 20.4. S. Hull and D. A. Keen, J. Phys.: Condens. Matter, 2001, 13, 5597.5. L. Eriksson, P. Wang and P.-E. Werner, Z. Kristallogr., 1991, 197, 235.6. H. Mikler, Monatsh. Chem., 1989, 120, 7.7. R. Sjovall and C. Svensson, Acta Crystallogr., 1988, C44, 207.8. J. Beck and S. Hedderich, J. Solid State Chem., 2000, 151, 73.9. H. Wiedemeier, M. A. Hutchins, Y. Grin, C. Feldmann and H. G. von
Schnering, Z. Anorg. Allg. Chem., 1997, 623, 1843.10. J. H. Kennedy, C. Schaupp, Y. Yang, Zhengming Zhang, T. Novinson and
T. Hoffard, J. Solid State Chem., 1990, 88, 555.
Molybdates
Name Formula MW Color Crystal structure Ref.
Mercury(I)molybdate
a-Hg2MoO4 561.116 1, 2b-Hg2MoO4 561.116 1Hg2Mo2O7 705.053 3Hg2Mo5O16 1136.864 3HgMoO4 360.526 Monoclinic 4
Inorganic and Organic Mercury Compounds 289
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1. T. J. Mormann and W. Jeitschko, Inorg. Chem., 2000, 39, 4219.2. A. L. Wessels, R. Czekalla and W. Jeitschko, Mater. Res. Bull., 1998,
33, 95.3. S. V. Borisov, S. A. Magarill, N. V. Pervukhina and N. A. Kryuchkova,
J. Struct. Chem., 2002, 43, 293.4. W. Jeitschko and A. W. Sleight, Acta Crystallogr., 1973, B29, 869.
Niobates
Name Formula MW Color Crystal structure Ref.
Hg2Nb2O7 698.992 Cubic 1
1. W. Sleight, Inorg. Chem., 1968, 7, 1704.
Nitrites, Nitrides and Nitrates
Name Formula MW ColorCrystalstructure Ref.
Mercury(I)nitrite
Hg2(NO2)2 493.19 1[(Hg2)2O(NO3)]NO3 �HNO3 1005.4 Orthorhombic 2[(Hg2)5(OH)4(NO3)2](NO3)4 2446.0 Triclinic 2[Hg2(OHg)2](NO3)2 958.4 Monoclinic 2
Basic mercurynitrate
Hg8O4(OH)(NO3)5 1995.743 3
K3[Hg(NO2)4]NO3 563.908 4
1. R. B. English, D. Rohm and C. J. H. Schutte, Acta Crystallogr., 1985, C41,997.
2. B. Kamenar, D. Matkovic-Calogovic and A. Nagl, Acta Crystallogr., 1986,C42, 385.
3. M. Weil, Z. Anorg. Allg. Chem., 2005, 631, 1346.4. D. Hall and R.V. Holland, Inorg. Chim. Acta, 3, 1969, 235.
Oxides, Oxalates and Oxomercurates
Name Formula MW. ColorCrystalstructure Ref.
Mercury(II)oxide
HgO 216.589 Triclinic See Appendix IHgO 216.589 Orthorhombic 1HgO 216.589 TetragonalHgO 216.589 CubicHgO 216.589 Hexagonala-HgO2 232.588 Rhombohedralb-HgO2 232.588Hg2O 417.179 Decomposes at
100 1CHg2O2NaI 583.072 1
290 Appendix III
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Name Formula MW. ColorCrystalstructure Ref.
Mercury(II)oxalate
C2HgO4 288.608 2Li2HgO2 246.47 Tetragonal 3Na2HgO2 278.568 Tetragonal 3K2HgO2 310.784 Tetragonal 3Rb2HgO2 403.524 Tetragonal 3Cs2HgO2 498.398 Tetragonal 3BaHgO2 369.918 Hexagonal 4BaHgO2 369.918 Rhombohedral 5SrHgO2 320.211 6CdHgO2 344.999 Monoclinic 7
1. K. Aurivillius, Acta Chem. Scand., 1964, 18, 1305.2. A. N. Christensen, P. Norby and J. C. Hanson, Z. Kristallogr., 1994,
209, 874.3. R. Hoppe and H. J. Rohrborn, Z. Anorg. Allg. Chem., 1964, 329, 110.4. M. Soll and H. Muller-Buschbaum, J. Less-Common Met., 1990,
162, 169.5. S. N. Putilin, S. M. Kazakov and M. Marezio, J. Solid State Chem., 1994,
109, 406.6. S. N. Putilin, M. G. Rozova, D. A. Kashporov, E. V. Antipov and L. M.
Kovba, Russ. J. Inorg. Chem., 1991, 36, 928.7. T. Hansen and H. Muller-Buschbaum, Z. Anorg. Allg. Chem., 1994, 620,
1137.
Phosphorus compounds
Name Formula MW ColorCrystalstructure Ref.
Mercury(II)pyrophosphatedihydrate
Hg2P2O7(H2O)2 611.151 Colorless 1
Mercury(I)dihydrogen-phosphate
Hg2(H2PO4)2 595.152 Monoclinic 2AgHg2PO4 604.018 Orthorhombic 3(Hg2)2(H2PO4)(PO4) 994.316 Yellowish Monoclinic 4
Mercury(I) phosphate a-(Hg2)3(PO4)2 1393.48 Orange Monoclinic 5b-(Hg2)3(PO4)2 1393.48 Orange Monoclinic 5
Mercury(II)polyphosphate
Hg(PO3)2 358.532 6
Mercury(II)phosphate
Hg3(PO4)2 791.71 Monoclinic 7
(Hg2)2P2O7 976.301 Lightyellow
Monoclinic 5
Mercury(II)diphosphate
Hg2P2O7 575.121 8
Mercury(II)hydrogenphosphate
HgHPO4 2185.213 Colorless Triclinic 9(Hg3)3(PO4)4 2057.198 Colorless Trigonal 10(Hg3)2(HgO2)(PO4)2 1626.068 Yellow Monoclinic 10
Inorganic and Organic Mercury Compounds 291
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1. M. Weil, Monatsh. Chem., 2003, 134, 1509.2. B. A. Nilsson, Z. Kristallogr., 1975, 141, 321.3. R. Masse, J.-C. Guitel and A. Durif, J. Solid State Chem., 1978,
23, 369.4. M. Weil, Z. Anorg. Allg. Chem., 626, 2000, 1752.5. M. Weil and R. Glaum, Z. Anorg. Allg. Chem., 1999, 625, 1752.6. M. Weil and R. Glaum, Acta Crystallogr., 2000, C56, 133.7. K. Aurivillius and B. A. Nilsson, Z. Kristallogr., 1975, 141, 1.8. M. Weil and R. Glaum, Acta Crystallogr., 1997, C53, 1000.9. E. Dubler, L. Beck, L. Linowsky and G. B. Jameson, Acta Crystallogr.,
1981, B37, 2214.10. M. Weil and R. Glaum, J. Solid State Chem., 2001, 157, 68.
Rhenates
Name Formula MW Color Crystal structure Ref.
HgReO4 450.793 1Hg5Re2O10 1535.354 1Hg5Re2O10 1535.354 1Hg2ReO5 667.382 1
1. S. V. Borisov, S. A. Magarill, N. V. Pervukhina and N. A. Kryuchkova,J. Struct. Chem., 2002, 43, 293.
Selenides and Selenates
Name Formula MW ColorCrystalstructure Ref.
HgSe 279.55 SeeAppendix I
Mercury(II)selenite
a-HgSeO3 327.547 1b-HgSeO3 327.547 Trigonal 2g-HgSeO3 327.547 Trigonal 2
Mercury(II)selenatemonohydrate
HgSeO4 �H2O 361.561 Monoclinic 3a-Hg2SeO3 528.137 Light
yellow4
b-Hg2SeO3 528.137 Colorless 4g-Hg2SeO3 528.137 4
Mercury(II)selenate(IV)
HgSeO4 343.546 Orthorhombic 5HgSeO4 �HgO 560.135 Monoclinic 5HgSeO4 � 2HgO 1168.122 Trigonal 5HgSeO3 �HgO � 1/6H2O
563.136 Trigonal 6
Hg3SeO6 776.724 5Hg3Se3O10 998.64 7Hg4Se4O9 1262.191 2
292 Appendix III
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1. M. Koskenlinna and J. Valkonen, Acta Crystallogr., 1995, C51, 1040.2. M. Weil, Solid State Sci., 2002, 4, 1153.3. C. Stalhandske, Acta Crystallogr., 1978, B34, 1408.4. M. Weil, J. Solid State Chem., 2003, 172, 35.5. M. Weil, Z. Naturforsch., 2002, 57B, 1043.6. M. Weil, Acta Crystallogr., 2002, C58, i164.7. M. Weil and Kolitsch, Acta Crystallogr., 2002, C58, i47.
Sulfides and Sulfates
Name Formula MW ColorCrystalstructure Ref.
a-HgS 232.656 See Appendix Ib-HgS 232.656 See Appendix I
Mercurychloride sulfide
a-Hg3Cl2S2 736.808 White Cubic 1
b-Hg3Cl2S2 736.808 WhiteMercury(II)sulfate
HgSO4 296.652 Orthorhombic 2Orthorhombic 3
HgSO4 �H2O 314.667 OrthorhombicOrthorhombic 4
Hg3(SO4)O2 729.83 5, 6HgSO4 � 2HgO 1121.225 7
Trimercury(II)dihydroxidedisulfatemonohydrate
Hg3(OH)2(SO4)2 �H2O
848.923 Monoclinic 8
Mercurymanganesesulfide
HgMnS 287.594 Cubic 9
Mercury ironsulfide
HgFeS 288.503 Cubic 9
Mercury cobaltsulfide
HgCoS 291.589 Cubic 9
1. H. Puff and J. Kuster, Naturwissenschaften, 1962, 49, 299.2. P. A. Kokkoros and P. J. Rentzeperis, Z. Kristallogr., 1963, 119, 234.3. C. Stalhandske, Acta Crystallogr., 1980, B36, 23.4. L. K. Templeton, D. H. Templeton and A. Zalkin, Acta Crystallogr., 1964,
17, 933.5. M. Weil, Acta Crystallogr., 2001, E57, i98.6. M. A. K. Ahmed, H. Fjellvag and A. Kjekshus, Thermochim. Acta, 2002,
390, 113.7. G. Nagorsen, S. Lyng, A. Weiss and A. Weiss, Angew. Chem., 1962,
74, 119.8. K. Aurivillius and C. Stalhandske, Z. Kristallogr., 1976, 144, 1.9. W. Paszkowicz, Powder Diffract., 2000, 15, 116.
Inorganic and Organic Mercury Compounds 293
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Tellurides and Tellurates
Name Formula MW ColorCrystalstructure Ref.
Mercury(II) bromidetelluride
Hg3Br2Te2 1016.778 Yellow 1, 2
Mercury chloride telluride Hg3Cl2Te2 927.875 Yellow 1Mercury telluride bromideiodide
Hg3Te2BrI 1063.778 Monoclinic 3Hg2TeO4 592.776 Monoclinic 4HgTeO4 � 2H2O 1020.330 Orthorhombic
Mercury(II) tellurite HgTeO3 376.187 Triclinic 5Mercury(II) tellurite(IV)tellurate(VI)
a-Hg2Te2O7 768.373 Monoclinic 6b-Hg2Te2O7 768.373 Orthorhombic 6
Mercury(II)orthotellurate(VI)
Hg3TeO6 825.364 Amber Cubic 7
Basic mercury(II)tetraoxotellurate(VI)
Hg2TeO5 608.775 Dark red Orthorhombic 7
Disilver(I) dimercury(II)tris[tetraoxotellurate(VI)]
Ag2Hg2(TeO4)3 1191.722 Red 8
1. H. Puff, et al., Naturwissenschaften, 1962, 49, 299.2. P. Khodadad, et al., Ann. Chim. (Paris), 1965, 10, 83.3. Yu. V Minets, Yu. V Voroshilov and V. V Pan’ko, J. Alloys Compd., 2004,
367, 109.4. G. Brandt and R. Moritz, Mater. Res. Bull., 1985, 20, 49.5. V. Kramer and G. Brandt, Acta Crystallogr., 1986, C42, 917.6. M. Weil, Z. Kristallogr., 2003, 218, 691.7. M.Weil, Z. Anorg. Allg. Chem., 2003, 629, 653.8. M. Weil, Acta Crystallogr., 2005, C61, i103.
Tantalates
Name Formula MW ColorCrystalstructure Ref.
Hg2Ta207 875.075 Cubic 1
1. A. W. Sleight, Inorg. Chem., 1968, 7, 1704.
Tungstates
Name Formula MW ColorCrystalstructure Ref.
Hg2WO4 649.026 Monoclinic 1, 2
1. A. L. Wessels, R. Czekalla and W. Jeitschko, Mater. Res. Bull., 1998,33, 95.
2. T. J. Mormann and W. Jeitschko, Inorg. Chem., 2000, 39, 4219.
294 Appendix III
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Vanadates
Name Formula MW Color Crystal structure Ref.
Mercury vanadate(IV,V) Hg2V8O20 1128.696 1Mercury(I) vanadate(V) HgVO3 299.529 Triclinic 2Mercury(I,II) vanadate Hg2VO4 516.118 2Mercury(II) vanadate(V) a-HgV2O6 398.468
b-HgV2O6 398.468 3, 4a-Hg2V2O7 615.057 5b-Hg2V2O7 615.057 6
1. M. Weil, B. Stoeger, A. L. Wessels and W. Jeitschko, Z. Naturforsch., 2007,62B, 1390.
2. S. V. Borisov, S. A. Magarill, N. V. Pervukhina and N. A. Kryuchkova,J. Struct. Chem., 2002, 43, 293.
3. J. Angenault and A. Rimsky, C. R. Acad. Sci. Ser. C, 1968, 266, 978.4. T. J. Mormann and W. Jeitschko, Z. Kristallogr. New Cryst. Struct., 2000,
216, 3.5. M. Quarton, J. Angenault and A. Rimsky, Acta Crystallogr., 1973, B29,
567.6. A. W. Sleight, Mater. Res. Bull., 1972, 7, 827.
Mixed Halides
Name Formula MW Color Crystal structure Ref.
Mercury bromide chloride a-HgBrCl 315.947 Orthorhombic 1Mercury bromide chloride b-HgBrCl 315.947 Orthorhombic 1Mercury bromide fluoride HgBrF 299.492 2Mercury bromide iodide HgBrI 407.398 3Mercury chloride iodide HgClI 362.947 3
1. S. Mehdi and S. Mumtaz Ansari, J. Solid State Chem., 1981, 40, 122.2. R. P. Rastogi, et al., J. Inorg. Nucl. Chem., 1975, 37, 1167.3. R. P. Rastogi and B. L. Dubey, J. Am. Chem. Soc., 1967, 89, 200.
Intercalation Compounds
Name Formula MW Color Crystal structure Ref.
Mg(NH3)6Hg22 1Hg–TiS2 2Hg1.24TiS2 3K–Hg–graphite 4Graphite–Hg–alkalis 5HgxTaS2 (x¼ 0.58, 1.19 and 1.3) 6
1. I.-C. Hwang, T. Drews and K. Seppelt, J. Am. Chem. Soc., 2000, 122, 8486.2. E. W. Ong, M. J. McKelvy, G. Ouvrard and W. S. Glaunsinger, Chem.
Mater., 1992, 4, 14.
Inorganic and Organic Mercury Compounds 295
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3. P. Ganal, P. Moreau, G. Ouvrard, M. Sidorov, M. McKelvy and W.Glaunsinger, Chem. Mater., 1995, 7, 1132.
4. G. Roth, A. Chaiken, T. Enoki, N. C. Yeh, G. Dresselhaus and P. M.Tedrow, Phys. Rev. B, 1985, 32, 533.
5. Y. Iye and S.-i. Tanuma, Phys. Rev. B, 1982, 25, 4583.6. P. Ganal, P. Moreau, G. Ouvrard, W. Olberding and T. Butz, Phys. Rev. B,
1995, 52, 11359.
296 Appendix III
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APPENDIX IV
Selected OrganometallicCompounds of Mercury
The physical properties of approximately 800 organomercury compounds havebeen summarized in Wardell [1]. Physical properties of selected organometalliccompounds are reviewed here. Most of these compounds are either highly toxicor extremely toxic and extreme care must be exercised in handling and usingany of these compounds.
Ethylmercury Compounds
Name Formula MW
Density
(g cm–3) CAS No. M.P. (1C) B.P. (1C) Ref.
Ethylmercury(II)
acetate
C4H8HgO2 288.71 109-62-6 69.9 117 1, 2
Ethylmercury(II)
bromide
C2H5HgBr 309.56 107-26-6 198 3, 4
Ethylmercury(II)
chloride
C2H5HgCl 265.10 107-27-7 196–198 1, 4
Ethylmercury(II)
hydroxide
C2H6HgO 246.66 107-28-8 37 1
Ethylmercury(II)
iodide
C2H5HgI 356.56 2440-42-8 186 5, 6
Methylmercury Compounds
Name Formula MWDensity(g cm–3) CAS No. M.P. (1C) B.P. (1C) Ref.
Methylmercury(II)acetate
C3H6HgO2 274.67 108-07-6 125.5–127.5 1, 7
Methylmercury(II)bromide
CH3HgBr 295.53 506-83-2 161–172 7
Methylmercury(II)chloride
CH3HgCl 251.08 115-09-3 167 4, 7
Mercury Handbook: Chemistry, Applications and Environmental Impact
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r L F Kozin and S C Hansen 2013
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Name Formula MWDensity(g cm–3) CAS No. M.P. (1C) B.P. (1C) Ref.
Methylmercury(II)cyanide
CH3HgCN 241.64 3.97 2597-97-9 93 1, 7, 8
Methylmercury(II)hydroxide
CH4HgO 232.63 1184-57-2 137 1, 7
Methylmercury(II)iodide
CH3HgI 342.53 143-36-2 152 9
Phenylmercury Compounds
Name Formula MWDensity(g cm–3) CAS No. M.P. (1C) B.P. (1C) Ref.
Diphenylmercury C12H10Hg 354.80 2.25meas
2.38X-ray587-85-9 124.5–125 1, 7,
10Diphenylethynylmercury
C16H10Hg 402.9 B2.0 6077-10-7 125 11
Phenylmercury(II)acetate
C6H8HgO2 336.74 2.4 62-38-4 149.5 1, 12
Phenylmercury(II)benzoate
C13H10HgO2 398.81 25358-71-8 97–98 220–240dec.
1
Phenylmercury(II)borate
C6H7BHgO3 338.52 102-98-7 112–113 13, 14
Phenylmercury(II)chloride
C6H5HgCl 313.18 100-56-1 249 14–16
Phenylmercury(II)bromide
C6H5HgBr 357.60 1192-89-8 283 15
Phenylmercury(II)hydroxide
C6H6HgO 294.70 100-57-2 197–205 14
Phenylmercury(II)iodide
C6H5HgI 404.60 823-04-1 269 15
Phenylmercury(II)nitrate
C6H5HgNO3 339.70 55-68-5 114.5–116.5 1
Phenylmercurynitrate, basic
C6H5HgOH-C6H5HgNO3
634.45 8003-05-2 175–185dec.
14
Phenylmercuryoleate
C6H5HgO-COC17H33
559.17 104-68-9 45 14
Other R2Hg Molecules
Name Formula MW
Density
(g cm–3) CAS No. M.P. (1C) B.P. (1C) Ref.
Dibenzylmercury C14H14Hg 382.86 2.17X-ray 780-24-5 111 17
Diethylmercury (C2H5)2Hg 258.71 2.45 627-44-1 –45 159 7
Dimethylmercury Hg(CH3)2 230.66 3.07 593-74-8 –43 96 14
Dipropylmercury C6H14Hg 286.77 2.02 628-85-3 189–191 1
Divinylmercury C4H6Hg 254.68 2.76 1119-20-6 157 1
References
1. J. L. Wardell (ed.), Organometallic Compounds of Zn, Cd and Hg,Chapman and Hall, London, 1985.
298 Appendix IV
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2. F. C. Whitmore, Organic Compounds of Mercury, Chemical Catalog Co.,New York, 1921.
3. C. S. Marvel, C. G. Gauerke and E. L. Hill, J. Am. Chem. Soc., 1925,47, 3009.
4. D. R. Grdenic and A. I. Kitaigorodskii, Zh. Fiz. Khim., 1949, 23, 1161.5. M. M. Baig, MSc thesis, University of British Columbia, 1961.6. E. Krause and A. Von Grosse, Die Chemie der Metal-Organischen
Verbindung, Borntraeger, Berlin, 1937.7. H. L. Roberts, Adv. Inorg. Chem. Radiochem, 1968, 11, 309–338.8. J. C. Mills, H. S. Preston and H. L. Kennard, J. Organomet. Chem., 1968,
14, 33.9. A. J. Brown, O. W. Howarth and P. J. Moore, J. Chem. Soc., Dalton
Trans., 1976, 1589.10. D. Grdenic, B. Kamenar and A. Nagl, Acta Crystallogr, 1977, B33, 587.11. J. Trotter, Can. J. Chem., 1962, 40, 1218.12. B. Kamenar, et al., Inorg. Chim. Acta, 1972, 6, 191.13. G. W. A. Milne, Drugs: Synonyms and Properties, Ashgate Publishing,
Brookfield, VT, 2000, p. 1280.14. M. Simon, P. Jonk, G. Wuhl-Couturier and S. Halbach,Mercury, Mercury
Alloys and Mercury Compounds, Wiley-VCH, Weinheim, 2006.15. V. I. Pakhomov, J. Struct. Chem, 1963, 4, 540.16. J. Fayos, G. Artioli and R. Torres, J. Chem. Crystallogr, 1993, 23, 595.17. P. B. Hitchcock, Acta Crystallogr, 1979, B35, 746.
Selected Organometallic Compounds of Mercury 299
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APPENDIX V
Solubility of Common Metalsin Mercury
Ag
T (1C) T (K) Mole fraction Ag Ref.
16.2 289.4 0.000558 120.0 293.2 0.00071 250.0 323.2 0.0016 299.6 372.8 0.004121 1100.0 373.2 0.0041 2150.0 423.2 0.0091 2184.4 457.6 0.034192 1200.0 473.2 0.018 2250.0 523.2 0.031 2260.0 533.2 0.0345 1275.0 548.2 0.044 2300.0 573.2 0.051 2306.0 579.2 0.0525 1338.0 611.2 0.0687 1350.0 623.2 0.120 2356.7 629.9 0.0929 1400 673 0.200 2405 678 0.1805 1450 723 0.290 2500 773 0.390 2550 823 0.440 2
1. D. R. Hudson, Metallurgia, 1943, 28, 203.2. G. Jangg and H. Palman, Z. Metallkd., 1963, 54, 364.
Mercury Handbook: Chemistry, Applications and Environmental Impact
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Al
T (1C) T (K) Mole fraction Al Ref.
76 349 0.001 1101 374 0.001 1103 376 0.001 1125 398 0.002 1160 433 0.003 1260 533 0.008 1312 585 0.013 1370 643 0.046 2460 733 0.100 2480 753 0.124 2510 783 0.204 2524 797 0.274 2542 815 0.355 2550 823 0.402 2558 831 0.447 2561 834 0.465 2566 839 0.500 2576 849 0.606 2582 855 0.667 2590 863 0.746 2595 868 0.805 2600 873 0.812 2604 877 0.854 2610 883 0.880 2643 916 0.882 2650 923 0.959 2652 925 0.986 2
1. H. A. Leibhafsky, J. Am. Chem. Soc., 1949, 27, 1468.2. C. J. De Gruyer, Recl. Trav. Chim. Pays-Bas, 1925, 44, 937.
Au
T (1C) T (K) Mole fraction Au Ref.
80.8 353.95 0.00467 1101.2 374.35 0.00697 1121.7 394.85 0.01211 1142.1 415.25 0.01482 1159.2 432.35 0.01847 1182.3 455.45 0.02434 1200.0 473.15 0.030 1219.6 492.75 0.037 1239.2 512.35 0.051 1260.2 533.35 0.065 1269.6 542.75 0.078 1279.6 552.75 0.081 1292.6 565.75 0.126 1299.5 572.65 0.140 1308 581 0.203 2328 601 0.300 2
Solubility of Common Metals in Mercury 301
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T (1C) T (K) Mole fraction Au Ref.
351 624 0.351 2375 648 0.401 2418 691 0.449 2
1. A. A. Sunier and E. B. Gramkee, J. Am. Chem. Soc., 1929, 51, 1703.2. C. Rolfe and W. Hume-Rothery, J. Less-Common Met., 1967, 13, 1.
Bi
T (1C) T (K) Mole fraction Bi Ref.
–35.4 237.75 0.001 1, 2–30.3 242.85 0.0015 1, 2–22.1 251.05 0.0022 1, 2–9.85 263.3 0.0036 1, 2–2.6 270.55 0.0046 1, 217.6 290.75 0.0097 1, 222.5 295.65 0.0112 1, 232.4 305.55 0.0175 1, 237.0 310.15 0.02 242.2 315.35 0.0275 1, 247.0 320.15 0.03 250.85 324.00 0.04 1, 254.0 327.15 0.04 261.6 334.75 0.058 1, 262.0 335.15 0.05 269.5 342.65 0.077 1, 271 344.15 0.08 279 352.15 0.11 281 354.15 0.13 286 359.15 0.15 290 363.15 0.17 296 369.15 0.2 2108 381.15 0.25 2118 391.15 0.3 2120 393.15 0.3 2135 408.15 0.4 2155 428.15 0.5 2170 443.15 0.6 2200 473.15 0.7 2
1. G. Petot-Ervas, P. Desre and E. Bonnier, C. R. Acad. Sci., 1965, 261,3406–3409.
2. G. Petot-Ervas, M. Allibert, C. Petot, P. Desre and E. Bonnier, Bull. Soc.Chim. Fr., 1969, 1477–1481.
Cd
T (1C) T (K) Mole fraction Cd Ref.
–36.4 236.8 0.0047 1–35.0 238.2 0.0080 2
302 Appendix V
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T (1C) T (K) Mole fraction Cd Ref.
–34.6 238.6 0.0094 1–34.0 239.2 0.0130 2–25.0 248.2 0.0200 2–19.0 254.2 0.0250 2–13.0 260.2 0.0300 2–10.0 263.2 0.0350 2–2.0 271.2 0.0500 2–1.6 271.6 0.0552 16.5 279.7 0.0650 212.5 285.7 0.0750 217.5 290.7 0.0850 225.0 298.2 0.0900 128.5 301.7 0.1050 234.0 307.2 0.1244 148.0 321.2 0.1550 250.0 323.2 0.1600 154.4 327.6 0.1839 157.0 330.2 0.1850 257.0 330.2 0.1840 165.5 338.7 0.2000 268.8 342.0 0.2221 174.0 347.2 0.2200 274.0 347.2 0.2221 175.0 348.2 0.2800 176.0 349.2 0.2400 284.6 357.8 0.2722 185.5 358.7 0.2750 286.0 359.2 0.2722 188.0 361.2 0.2800 2117.0 390.2 0.3839 1121.8 395.0 0.4004 1149.6 422.8 0.5028 1150.0 423.2 0.5028 1163.6 436.8 0.5510 1190.8 464.0 0.6433 1214.6 487.8 0.7090 1221.0 494.2 0.7090 1234.0 507.2 0.7450 1237.3 510.5 0.7458 1273.4 546.6 0.8496 1
1. H. C. Bijl, Z. Phys. Chem., 1902, 41, 641.2. R. E. Mehl and C. S. Barrett, Trans. AIME, 1930, 89, 575.
Co
T (1C) T (K) Mole fraction Co Ref.
160 433.15 2.00�10–8 1500 773.15 6.80�10–7 1525 798.15 6.50�10–7 3–5550 823.15 8.20�10–7 2
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T (1C) T (K) Mole fraction Co Ref.
550 823.15 1.80�10–6 3–5575 848.15 2.70�10–6 3–5600 873.15 1.40�10–6 3–5625 898.15 1.40�10–6 3–5650 923.15 4.10�10–6 3–5675 948.15 2.40�10–6 3–5700 973.15 7.10�10–6 3–5725 998.15 6.10�10–6 3–5750 1023.15 1.10�10–5 3–5
1. J. Borodzinski, University of Warsaw, unpublished data, personalcommunicaton to C. Guminski, 1987.
2. G. Jangg and H. Palman, Z. Metallkd., 1963, 54, 364.3. J. R. Weeks, A. Minardi and S. Fink, USAEC Report, BNL-841, 1963,
p. 76.4. J. R. Weeks and S. Fink, USAEC Report, BNL-900, 1964, pp. 136–138.5. J. R. Weeks, Corrosion, 1967, 23, 98.
Cu
T (1C) T (K) Mole fraction Cu Ref.
20 293.15 0.0001 150 323.15 0.00023 160 333.15 0.00025 280 353.15 0.00037 2100 373.15 0.00048 2150 423.15 0.0011 3250 523.15 0.0034 3350 623.15 0.0076 3450 723.15 0.0153 3550 823.15 0.0360 3
1. S. A. Levitskaya and A. I. Zebreva, Trans. Inst. Khim. Akad. Nauk Kazakh.SSR, 1967, 15, 66.
2. A. A. Lange, S. P. Bukhman and A. A. Kairbaeva, Izv. Akad. Nauk Kazakh.SSR, Ser. Khim., 1974, 24, 37.
3. G. Jangg and H. Palman, Z. Metallkd., 1964, 54, 364.
Cr
T (1C) T (K) Mole fraction Cr Ref.
500 773 0.0120 1500 773 0.0083 2505 778 0.0118 2
1. G. Jangg and H. Palman, Z. Metalld., 1963, 54, 364.2. J. R. Weeks, Corrosion, 1967, 23, 98.
304 Appendix V
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Fe
T (1C) T (K) Mole fraction Fe Ref.
25 298 5.4�10–6 1100 373 6.8�10–6 1200 473 1.1�10–5 1300 573 1.9�10–5 1400 673 4.0�10–5 1500 773 7.5�10–5 1600 873 1.6�10–4 1700 973 3.4�10–4 1
1. A. L. Marshall, L. F. Epstein and F. J. Norton, J. Am. Chem. Soc., 1950, 72,3514.
Gd
T (1C) T (K) Mole fraction Gd Ref.
25 298 9.8�10–5 125 298 5.3�10–5 292.5 365.5 0.000377 3132.5 405.5 0.00081 3147.5 420.5 0.00121 3150 423 0.0013 4207.5 480.5 0.0027 3215.0 488 0.00274 3282.5 555.5 0.00664 3295.0 568 0.00533 3340.0 613 0.00967 3450 723 0.013 4
1. V. A. Bulina, A. I. Zebreva and R. Sh. Enikeev, Izv. V. U. Z. Khim. Khim.Tekhnol., 1977, 20, 959.
2. V. A. Bulina, L. V. Guminichenko, A. I. Zebreva and R. Sh. Enikeev,Radiokhimiya, 1977, 19, 89.
3. A. E. Messing and O. C. Dean, USAEC Rep., ORNL-2871, 1960.4. H. Kirchmayr and W. Lugscheider, Z. Metallkd., 1966, 57, 725.
In
T (1C) T (K) Mole fraction In Ref.
25 298 0.700 137 310 0.725 153 326 0.750 166 339 0.775 180 353 0.8025 190 363 0.825 1101 374 0.850 1103 376 0.855 1106 379 0.860 1
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T (1C) T (K) Mole fraction In Ref.
108 381 0.875 1114 387 0.880 1123 396 0.900 1134 407 0.936 1150 423 0.975 1
1. L. F. Kozin and N. N. Tananaeva, Russ. J. Inorg. Chem., 1961, 6, 463.
Mn
T (1C) T (K) Mole fraction Mn Ref.
20 293 4.6�10–5 120 293 4.6�10–5 225 298 4.4�10–5 325 298 4.4�10–5 430 303 6.2�10–5 586 359 0.00087 6100 373 0.0010 6114 387 0.0012 6125 398 0.0017 6148 421 0.0026 6166 439 0.0031 6198 471 0.0036 6225 498 0.0051 6246 519 0.0069 6270 543 0.0087 6300 573 0.013 6330 603 0.019 6350 623 0.022 6370 643 0.026 6400 673 0.031 6418 691 0.036 6450 723 0.046 6470 743 0.056 6500 773 0.063 6552 825 0.076 6565 838 0.082 6
1. N. M. Irvin and A. S. Russell, J. Chem. Soc., 1932, 891.2. W. Kemula and Z. Galus, Roczn. Chem., 1962, 36, 1223.3. I. E. Krasnova and A. I. Zebreva, Elektrokhimiya., 1966, 2, 96.4. T. Hurlen and R. Smaaberg, J. Electroanal. Chem., 1976, 71, 157.5. J. F. deWet and R. A. W. Haul, Z. Anorg. Allg. Chem., 1954, 277, 96.6. G. Jangg and H. Palman, Z. Metallkd., 1963, 54, 364.
Pb
T (1C) T (K) Mole fraction Pb Ref.
–36 237.00 0.0044 1–15 258.00 0.0075 10 273.00 0.0096 1
306 Appendix V
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T (1C) T (K) Mole fraction Pb Ref.
15 288.00 0.0131 119.7 292.70 0.01469 224.0 297.00 0.015 324.9 297.90 0.0153 325 298.00 0.0165 425 298.00 0.0162 125.4 298.40 0.0154 326.3 299.30 0.0157 328.0 301.00 0.0161 330.7 303.70 0.01811 239.9 312.90 0.02203 247.4 320.40 0.02588 248.2 321.20 0.02631 250 323.00 0.0269 160.6 333.60 0.03438 269.2 342.20 0.04279 2115 388.00 0.25 5120 393.00 0.275 5137 410.00 0.35 5145 418.00 0.40 5164 437.00 0.475 5172 445.00 0.50 5184 457.00 0.55 5198 471.00 0.60 5202 475.00 0.625 5264 537.00 0.85 5273 546.00 0.875 5278 551.00 0.90 5293 566.00 0.95 5308 581.00 0.975 5
1. A. S. Moshkevich and A. A. Ravdel, Zh. Prikl. Khim., 1970, 43, 71.2. H. E. Thompson, J. Phys. Chem., 1935, 39, 655.3. P. Dumas, L. Bougarfa and J. Bensaid, J. Phys., 1984, 45, 1543.4. M. M. Haring, M. R. Hatfield and P. T. Zapponi, Trans. Electrochem. Soc.,
1939, 75, 473.5. G. V. Yan-Sho-Syan, M. V. Nosek, N. M. Semibratova and A. E.
Shalamov, Tr. Inst. Khim. Nauk Akad. Nauk Kazakh. SSR, 1967, 15, 139.
Pd
T (1C) T (K) Mole fraction Pd Ref.
25 298 0.000055 125 298 0.000050 241 314 0.000053 257 330 0.000058 281 354 0.000074 290 363 0.000089 295 368 0.000089 298 371 0.000094 2120 393 0.00016 2
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T (1C) T (K) Mole fraction Pd Ref.
135 408 0.00021 2161 434 0.00032 2162 435 0.00036 2175 448 0.00047 2200 473 0.00068 2214 487 0.00081 2226 499 0.00117 2234 507 0.0014 2240 513 0.0017 2253 526 0.0019 2260 533 0.0020 2286 559 0.0031 2305 578 0.0042 2
1. J. N. Butler and A. C. Makrides, Trans. Faraday Soc., 1964, 60, 938.2. G. Jangg and W. Groll, Z. Metallkd., 1965, 56, 232.
Pu
T (1C) T (K) Mole fraction Pu Ref.
19 292 0.000 136 121 294 0.000 131 224 297 0.000 161 250 323 0.000 255 2100 373 0.000 625 2150 423 0.00126 2190 463 0.00182 2200 473 0.00190 2225 498 0.00275 2260 533 0.00380 2280 553 0.00421 2300 573 0.00496 2325 598 0.00561 2
1. A. G. White, The Preparation of Plutonium Amalgam and Its Reaction withDilute Hydrochloric Acid, Tecnical Report AERE-C/R-1468, AtomicEnergy Research Establishment, Harwell, 1955.
2. D. F. Bowersox and J. A. Leary, J. Inorg. Nucl. Chem., 1959, 9, 108.
Rh
T (1C) T (K) Mole fraction Rh Ref.
500 773 1�10–6 1
1. G. Jangg and T. Dortbudak, Z. Metallkd., 1973, 64, 715.
Sn
T (1C) T (K) Mole fraction Sn Ref.
–35.4 237.75 0.0016 1–28.4 244.75 0.0029 1
308 Appendix V
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T (1C) T (K) Mole fraction Sn Ref.
–17.9 255.25 0.0041 1–8.4 264.75 0.0052 11.1 274.25 0.0065 116.5 289.65 0.0097 126 299.15 0.0127 130 303.15 0.0140 140 313.15 0.0188 150 323.15 0.0259 160 333.15 0.0334 172 345.15 0.0560 154 327.15 0.025 161 334.15 0.030 167.5 340.65 0.040 170 343.15 0.050 178 351.15 0.080 181.5 354.65 0.126 285 358.15 0.15 188.75 361.90 0.020 292 365.15 0.20 193.5 366.65 0.254 297 370.15 0.267 298 371.15 0.285 2101.5 374.65 0.308 2102 375.15 0.318 2103 376.15 0.30 1105 378.15 0.333 2108 381.15 0.362 2108.5 381.65 0.35 1113.5 386.65 0.40 1114 387.15 0.399 2117.5 390.65 0.418 2122.75 395.90 0.454 2123 396.15 0.45 1129 402.15 0.50 1132.5 405.65 0.500 2140.5 413.65 0.543 2142.5 415.65 0.55 1152 425.15 0600 2159.25 432.40 0.638 2166 439.15 0.668 2170.5 443.65 0.691 2180 453.15 0.736 2185.25 458.40 0.765 2192.5 465.65 0.800 2199.75 472.90 0.838 2207.5 480.65 0.879 2211.7 484.85 0.900 2215.5 488.65 0.922 2218.2 491.35 0.937 2221 494.15 0.952 2224 497.15 0.970 2227 500.15 0.983 2229.4 502.55 0.993 2
Solubility of Common Metals in Mercury 309
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1. G. Petot-Ervas, M. Gaillet and P. Desre, C. R. Acad. Sci., 1967, 264, 490.2. N. A. Puschin, Z. Anorg. Allg. Chem., 1903, 36, 210.
Tl
T (1C) T (K) Mole fraction Tl Ref.
0.5 273.5 0.4050 1184 457 0.7252 1218 491 0.7959 1231 504 0.8316 1244 517 0.8685 1261 534 0.9083 1278 551 0.9462 1283 556 0.9682 1
1. Y. Claire and J. Rey, J. Less-Common Met., 1980, 70, 33.
Tm
T (1C) T (K) Mole fraction Tm Ref.
25 298 4�10–6 1
1. V. A. Bulina, A. I. Zebreva and R. Sh. Enikeev, Izv. V. U. Z. Khim. Khim.Tekhnol., 1977, 20, 959.
Zn
T (1C) T (K) Mole fraction Zn Ref.
–41.50 231.65 0.0260 10.30 273.45 0.0409 213.00 286.15 0.0570 119.90 293.05 0.0586 230.00 303.15 0.0696 236.00 309.15 0.0840 139.95 313.10 0.0828 250.00 323.15 0.0966 251.50 324.65 0.1060 164.75 337.90 0.1206 272.00 345.15 0.1420 180.10 353.25 0.1480 288.25 361.40 0.1800 189.50 362.65 0.1662 294.80 367.95 0.1779 299.60 372.75 0.1885 2103.50 376.65 0.2150 1120.00 393.15 0.2510 1134.75 407.90 0.2860 1155.00 428.15 0.3340 1172.25 445.40 0.3710 1184.00 457.15 0.4000 1196.75 469.90 0.4320 1
310 Appendix V
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T (1C) T (K) Mole fraction Zn Ref.
209.75 482.90 0.4640 1223.75 496.90 0.5000 1233.50 506.65 0.5270 1246.75 519.90 0.5610 1262.25 535.40 0.6000 1274.50 547.65 0.6320 1285.00 558.15 0.6670 1300.00 573.15 0.7050 1317.00 590.15 0.7500 1325.75 598.90 0.7720 1334.00 607.15 0.7960 1342.50 615.65 0.8250 1354.00 627.15 0.8490 1372.00 645.15 0.8940 1396.00 669.15 0.9490 1
1. N. A. Pushin, Z. Anorg. Chem., 1903, 34, 201.2. E. Cohen and K. Inouye, Z. Phys. Chem., 1910, 71, 625
Zr
T (1C) T (K) Mole fraction Zr Ref.
350 623 1.1�10–3 1350 623 1.6�10–3 2, 3482 755 2.2�10–3 4500 773 6.6�10–3 5525 798 5.5�10–3 5–7545 818 3.4�10–3 5–7550 823 0.016 5572 845 3.7�10–3 5–7600 873 9.9�10–3 5–7600 873 0.012 5–7625 898 0.033 5–7650 923 0.043 5–7700 973 0.145 5–7760 1033 0.40 8
1. A. J. Nerad, General Electric Co., unpublished work, cited by L. R.Kelman, W. D. Wilkinson and F. L. Yagee, Resistance of Materials toAttack by Liquid Metals, USAEC Rep., ANL-4417, 1950, p. 68.
2. J. A. Leary, USAEC Rep., LA-2218, 1958.3. J. A. Leary, R. Benz, D. F. Bowersox, C. W. Bjørklund, K. W. H. Johnson,
W. J. Maraman, L. J. Mullins and J. G. Reavis, Pyrometallurgical purifi-cation of Pu reactor fuels, in Peaceful Uses of Atomic Energy, UnitedNations, Geneva, 1958, vol. 17, pp. 376–382.
4. J. F. Nejedlik, USAEC Rep., NAA-SR-6306, 1961.5. J. R. Weeks, Corrosion, 1967, 23, 98.6. J. R. Weeks and S. Fink, USAEC Rep., BNL-782, 1962, pp. 73–75.7. J. R. Weeks and S. Fink, USAEC Rep., BNL-900, 1964, pp. 136–38.8. A. Fleitman and J. Brandon,USAEC Rep., BNL-799, 1963, pp. 75–76.
Solubility of Common Metals in Mercury 311
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Subject Index
amalgam solubilitycompounds formation, solid
phasecalculation methods, 45empirical equation, 40–41Gibbs free energy, 41metal–metal bondenergy, 46
nickel solubility, 41, 43physicochemicalproperties, 41, 42
platinum solubility, 44rare earth metals, 45solubility curves, 43, 44temperaturedependence, 40
mercury metalschemical potential of, 36Gibbs free energy, 37, 39ideal mercurysolution, 39–40
physicochemicalproperties, 36
quantitativeassessment, 38
Schroder’s equation, 38thermodynamicequilibrium, 37
atomic absorption spectrometry(AAS), 152
binary amalgam systemsdensity and surface tension
Bi–Hg, 272Cd–Hg, 273
Cs–Hg, 273–274In–Hg, 274–275K–Hg, 275–276Na–Hg, 276Pb–Hg, 277–278Rb–Hg, 278Sn–Hg, 278–279Tl–Hg, 280Zn–Hg, 281
intermetallic phasesAg–Hg, 249Au–Hg, 249Ba–Hg, 250Br–Hg, 250Ca–Hg, 251Cd–Hg, 251Ce–Hg, 252Cl–Hg, 252Cs–Hg, 252Cu–Hg, 253Dy–Hg, 253Er–Hg, 254Eu–Hg, 254F–Hg, 254Ga–Hg, 255Hf–Hg, 255Ho–Hg, 255I–Hg, 256In–Hg, 256K–Hg, 256–257La–Hg, 257Li–Hg, 258Lu–Hg, 258Mg–Hg, 258–259Mn–Hg, 259
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Na–Hg, 259–260Nd–Hg, 261Ni–Hg, 261O–Hg, 261Pb–Hg, 262Pd–Hg, 262Po–Hg, 262Pr–Hg, 263Pt–Hg, 263Pu–Hg, 263Rb–Hg, 264Rh–Hg, 264Sc–Hg, 265Se–Hg, 265S–Hg, 265Sm–Hg, 266Sn–Hg, 266Sr–Hg, 267Tb–Hg, 267Te–Hg, 268Th–Hg, 268Ti–Hg, 269Tl–Hg, 269Tm–Hg, 269U–Hg, 270Yb–Hg, 270Y–Hg, 270Zn–Hg, 271Zr–Hg, 271
phase diagrams, 248
chalcogenidesepitaxial layer growth
annealing, 176ion implantation, 175thermal zinc ‘shift’method, 174
oxidation–reductionreactions, 172
transport reactionsmethod, 172–174
chlor-alkali processchlorine production
amalgam concentrationrange, 187
average linear flow rate, 188
cathode potential vs.amalgamconcentration, 187
current efficiency, 188graphite electrodes, 189hydrogen content, 187hydrogen dischargecurrent density, 188
medium-capacityindustrialelectrolyzers, 190
mercury cathodeelectrolysis, 189
ORTA, 185P-101 mercuryelectrolyzer, 190
polarized cathodepotentials, 186
sodium amalgam andcurrent density, 186
sodium amalgamdecomposer, 191
diaphragm and membraneprocess, 180
mercury cathode process,electrochemistry, 180–181
sodium–mercury phase diagramactivities of, 182, 183Gibbs free energy andentropy, 185
intermetallic compounds,thermodynamiccharacteristics, 185
mercury cell process, 184,185
sodium amalgamsystems, 182
structure of, 181, 182zero charge potential, 183
Comprehensive EnvironmentalResponse, Compensation, andLiability Act (CERCLA), 202
Cross-State Air Pollution Rule(CSAPR), 206–207
CSAPR see Cross-State Air PollutionRule (CSAPR)
313Subject Index
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demercurization processairborne mercury vapor
content, 236chlor-alkali plant
catastrophic effects, 229PavlogradKhimprom, 228–229
plexiglas sheet, 230wastewatercomposition, 229–230
chlorine-releasing reaction, 236contaminated surface, 235disproportionation
reaction, 236equilibrium constants, HClO
and mercury, 236–237fluorescent lamps see
fluorescent lampsmercury removal, industrial
wastewater, 234–235mono- and divalent
compounds, 228oxidizing properties, 235personal protection and
preventive measures, 237Department of Transportation
(DOT), 207–208DOT see Department of
Transportation (DOT)
electrochemical propertiescharacteristic transfer time, 130complex-forming media, 138,
140current density, 129disproportionation
reaction, 130electroreduction, cathodic
process, 129half-wave potential, 134Hg(II) diffusion coefficient, 137intermetallic
compounds, 134–135kinetic equation, 129kinetic parameters, 138, 139Luther equation, 131
monovalent mercury ions, 128Nernst equations, 134perchloric and nitric acids, 128positive electrode potential, 128reproportionation, 133ring-disk electrode, 135–136
oxidation current, 136rotation speed, 136, 137
second-order dimerization, 129single-electrode transfer, 137single-electron reaction, 130sodium sulfate, anodic
current, 138standard electrode
potential, 131sulfuric acid solution, 135transfer coefficients, 130voltamperometric
curve, 131–132S-shaped waves, 132, 133
Emergency Planning and CommunityRight-to-Know Act, 203–204
fluorescent lampsamalgam-controlled mercury
vapor pressure, 146–148AAS, 152KEMS, 152VPMS, 151
high-CRI fluorescent lampspectrum, 144, 145
mercury consumptionmechanisms, 146
mercury dispensersBi–Sn–Hgamalgams, 149–151
Ti–Hg amalgams, 151mercury dose per lamp, 146,
147operation of, 144, 145recycling
hydrometallurgicaltreatment, 233–234
operating lifetime, 230thermal demercurization,230–232
314 Subject Index
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vibration–pneumaticdemercurizationmethod, 232–233
sub-optimum efficacy, 146temperature-controlled
amalgamsmercury quantity, 147Sn–Hg amalgams,149, 150
Zn–Hgamalgams, 147–149
Food and Drug Administration(FDA), 204
Gibbs free energy, 37, 39, 41
halides and pseudohalidescalomel (Hg2Cl2)
enthalpy of, 89solubility product, 90thermodynamic andphysical properties,89, 90
HgBr2, 87acid–base interaction, 99equilibrium reaction,100
physical properties,101, 102
reverse reaction, 101solubility values,98, 101
vapor pressure, 97Hg2Br2
crystal structure, 97, 99phase diagram, 97, 99physical properties,96, 98
solubility productvalues, 97, 100
temperaturedependence, 96
HgCl2, 86–87corrosive sublimate seemercury(II) chloride(HgCl2)
Hg(CN)2equilibrium constant,107–108
physical properties,106, 107
sodium cyanide, 108HgF2, 87–89Hg2F2
Hg2X4 coordination,87, 88
physical properties, 87, 88HgI2
aqueous solubility,103, 104
HgI2–H2O phasediagram, 103, 104
orange HgI2, 105–106physical properties,103, 105
solid-statetransformations,103, 104
yellow HgI2, 103–105Hg2I2
physical properties,101, 102
potassium iodidesolutions, 103
solubility product,102, 103
Hg(SCN)2, 108–109Hg2(SCN)2, 108mixed mercury(II) halides, 106,
107Hall coefficient, 26, 27high-pressure sodium (HPS) lamps
color rendering index, 155data analysis, 155–156electrical and light
characteristicsNa–Cs–Hg, 157, 158with Tl and In, 156
excitation levels, 154–155physicochemical and spectral
characteristics, 155sodium amalgams, 154
315Subject Index
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high-pressure sodium (HPS) lamps(continued)
sodium–mercury binarysystem, 156
thallium effect, 157HPS lamps see high-pressure sodium
(HPS) lamps
IATA see International AirTransport Association (IATA)
inorganic and organic mercurycompounds
amido compounds, 282antimonides, 283arsenides and
arsenates, 282–283azides, 283borates, 283bromides and bromates, 284chlorides and chlorates, 285chromates, 286cyanides and cyanates, 287cyanimides and carbonates,
284fluorides, 288intercalation compounds, 295iodides and iodates, 288iodomercurates, 289mixed halides, 295molybdates, 289niobates, 290nitrites, nitrides and
nitrates, 290oxides, oxalates and
oxomercurates, 290–291phosphorus compounds, 291rhenates, 292selenides and selenates, 292sulfides and sulfates, 293tantalates, 294tellurides and tellurates, 294tungstates, 294vanadates, 295
inorganic mercury compoundsHg2
2+ and Hg2+, 80–81in ionic solutions
electron spin resonancespectra, 86
Hg2Cl2 solubility, 84reproportionationreaction, 86
standard electrodepotentials andtemperaturecoefficients, 85
thermodynamicparameters, 86
metallic mercury solubility,water, 82
elevated temperatures andpressures, 83, 84
Henry constant, 83solubility inversion, 83temperature range, 81
International Air TransportAssociation (IATA), 207–208
Knudsen effusion mass spectrometry(KEMS), 152
lightingdischarge light sources, 143,
144fluorescent lamps, 143high-pressure mercury
lamps, 143, 152HPS lamps, 143
color rendering index,155
data analysis, 155–156electrical and lightcharacteristics, with Tland In, 156
excitation levels,154–155
light and electricalcharacteristics,Na–Cs–Hg, 157, 158
physicochemical andspectralcharacteristics, 155
sodium amalgams, 154
316 Subject Index
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sodium–mercury binarysystem, 156
thallium effect, 157lamp color and quality
measurements, 144light quality and lamp operating
temperature, 144metal halide lamps, 143,
157–159UHP lamps, 143, 153–154
Lorentz number, 8
maximum achievable controltechnology (MACT), 201
MEBA see Mercury Export Ban Act(MEBA)
Mercury and Air Toxics Standards(MATS), 207
Mercury-Containing andRechargeable Battery ManagementAct, 201
Mercury Export Ban Act (MEBA)mercury compounds, 200provisions, 201
mercury(I) bromide (Hg2Br2)crystal structure, 97, 99phase diagram, 97, 99physical properties, 96, 98solubility product values,
97, 100temperature dependence, 96
mercury(I) chloride (Hg2Cl2)enthalpy of, 89solubility product, 90thermodynamic and physical
properties, 89, 90mercury(I) dithiocyanate
(Hg2(SCN)2), 108mercury(I) fluoride (Hg2F2)
Hg2X4 coordination, 87, 88physical properties, 87, 88
mercury(II) bromide (HgBr2)acid–base interaction, 99equilibrium reaction, 100physical properties, 101, 102reverse reaction, 101
solubility values, 98, 101vapor pressure, 97
mercury(II) chloride (HgCl2)complex ions yield, 95, 96enthalpy change, 94equilibrium reaction
constants, 91, 93–95formation constants, 95, 100mercury dihalides, 95molar solubility, 96physical properties, 96, 97solubility calculation, 91standard thermodynamic
functions, 94vapor pressure, 90in water, 91, 92
mercury(II) cyanide (Hg(CN)2)equilibrium constant, 107–108physical properties, 106, 107sodium cyanide, 108
mercury(II) dithiocyanate(Hg(SCN)2), 108–109
mercury(II) fluoride (HgF2), 87–89mercury(II) iodide (HgI2)
aqueous solubility, 103, 104HgI2–H2O phase diagram,
103, 104orange HgI2, 105–106physical properties, 103, 105solid-state
transformations, 103, 104yellow HgI2, 103–105
mercury(II) nitrate(Hg(NO3)2), 114–115
mercury(I) iodide (Hg2I2)physical properties, 101, 102potassium iodide solutions, 103solubility product, 102, 103
mercury(II) oxide (HgO)acidic solutions, 112alkaline solutions, 112characteristic structure,
110, 111density, 110for dissociation
pressure, 113–114
317Subject Index
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mercury(II) oxide (HgO) (continued)equilibrium constants,
111, 113hydrolysis reactions, 111linkage of, 114Pourbaix diagram, 113solubility of, 112standard half-reaction
potentials, 111thermodynamic properties,
R2Hg and RHgX, 113mercury(II) perchlorate Hg(ClO4)2,
116mercury(I) nitrate dihydrate
(Hg2(NO3)2 � 2H2O), 114–115mercury(I) oxide (Hg2O), 109–110mercury(I) perchlorate Hg2(ClO4)2,
116mercury legislation, United States
Acts of Congress, 199CERCLA, 202Clean Air Act, 201Clean Water Act, 202CSAPR, 206–207DOT, 207–208Emergency Planning and
Community Right-to-KnowAct, 203–204
Environmental ProtectionAgency, 201
FDA, 204IATA, 207–208MACT, 201MATS, 207MEBA
mercury compounds, 200provisions, 201
Mercury-Containing andRechargeable BatteryManagement Act, 201
NESHAP rule, 206OSHA, 207RCRA, 203, 205Safe Drinking Water Act, 203SARA, 202SNUR, 204
TMDL Regulations andGuidance, 205
TSCA, 203metallic mercury
atomic propertiesatomic radii, 2electron affinity, 2electronegativity values, 2electronic configuration, 1natural mercuryisotopes, 1
thermal neutron capturecross-section, 2
boiling point, 9chronic exposure, 242–243crystallography
P–T diagram, 3–4rhombohedralstructure, 3
densitygaseous mercury, 15–17pure mercury vs.pressure, 17, 18
of solid and liquidmercury, 14–17
solid and liquid mercuryvs. temperature, 14, 16
temperature andpressure, 16, 17
volume change, 14, 16electrical and magnetic
propertiesmagneticsusceptibility, 26
polynomial function, 25resistivity, liquid mercuryvs. temperature, 24, 25
resistivity, solid mercuryvs. temperature, 24, 25
temperature dependence,resistivity, 24, 26
emissivity, 9enthalpy and entropy of
evaporation, 9excited electronic states, 27–28Hall coefficient, 26, 27
318 Subject Index
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heat capacityDebye temperature, 5lattice vibrationcontribution, 5
least-squares analysis, 6molar heat capacity, 5, 7specific heat capacity, 6, 7temperature ranges, 4–5vacancy contribution, 6
heat of evaporation, 9heat of fusion, 4isothermal compressibility, 19, 21melting point, 4mercury vapor, 9preventive measures, 245–247self-diffusion
Arrhenius equations, 21Avogadro’s number, 23coefficients of, 23, 24constants, puremercury, 21, 22
dynamic viscosity, 23hydrodynamic masstransfer theory, 22–23
least-squares analysis, 22liquid mercury, 21, 22Stokes–Einsteinrelation, 23
superconductivity, 27surface tension, 17–18surveillance programs, 243–244thermal conductivity
conduction electrons, 8Lorentz number, 8mercury single crystals, 6
thermal expansioncoefficient, 20–21
toxicity of, 241vapor pressure
critical temperature andpressure, 14, 15
diatomic molecules, 10liquid mercury, 12, 13solid mercury, 10, 11triple point, 13–14
viscosity, 18–20
metals diffusion, 57atomic radius effect‘elementary’ metals, 51
intermetallic compoundformation, 52–53
lanthanides, 53particles diffusion, realradii, 52
surface viscosity, 53–54concentration effects
capillary method, 55–56In–Hg system, 56thallium, diffusioncoefficient, 56
upper and lower limits, 55diffusion coefficients, 50, 51Einstein-Sutherland
relation, 50size factor, 50in solid metals, 57–58Stokes–Einstein relation, 50temperature dependence,
amalgams, 54–55metals solubility
In, 305–306Ag, 300Al, 301Au, 301–302Bi, 302Cd, 302–303Co, 303–304Cr, 304Cu, 304Fe, 305Gd, 305Mn, 306Pb, 306–307Pd, 307–308Pu, 308Rh, 308Sn, 308–309Tl, 310Tm, 310Zn, 310–311Zr, 311
mixed mercury(II) halides, 106, 107
319Subject Index
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National Emission Standards forHazardous Air Pollutants(NESHAP) rule, 206
Nokitosk Mercury Plant, 61
Occupational Safety and HealthAdministration (OSHA), 207
organometallic compoundsethylmercury compounds, 297methylmercury
compounds, 297–298phenylmercury
compounds, 298R2Hg Molecules, 298
organometallic mercury (I)compounds, 116–117
organometallic mercury (II)compounds
addition reactions, 118amalgamation reactions, 118Grignard reactions, 118mercurization reactions, 118mercury(I) acetate, 119oxalate solutions, 119solvation energy, 117substitution reactions, 118
oxides of ruthenium and titaniumanodes (ORTA), 185
oxygen compoundsHg2(ClO4)2, 116Hg(ClO4)2, 116Hg(NO3)2, 114–115Hg2(NO3)2 � 2H2O, 114–115HgO
acidic solutions, 112alkaline solutions, 112characteristicstructure, 110, 111
density, 110for dissociationpressure, 113–114
equilibriumconstants, 111, 113
hydrolysis reactions, 111linkage of, 114Pourbaix diagram, 113
solubility of, 112standard half-reactionpotentials, 111
thermodynamicproperties, R2Hg andRHgX, 113
Hg2O, 109–110
purification methodschemical methods
air blasting and chemicaltreatment, 71
Bi3+ ions, electrostaticrepulsion effect, 70
cadmium ionconcentration, 69–70
decontamination, 74–75equilibrium exchangereactions, 67–68
exchange reaction rate,69
first-order kinetics, 68gold change potential,65, 67
high-performancechemical treatmentinstallation, 71–72
impurities oxidation, 62impurity separationcoefficient, 72
ion-exchange resin, 72magnetohydrodynamicpumps, 73
mechanical impurities, 63mercury half-reactions, 64nitric acidconcentration, 71
ozone-based dryprocess, 63
phase exchange rateconstants, 69
polarization curves, 69post-treatment impuritycontents, 72
standard electrodepotentials, 64–67
320 Subject Index
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treatment process,phases, 73–74
wet chemical treatmentmethods, 63
zinc ions, 70single-stage electrochemical
methods, 75–77technical requirements
crude organic substancesand gases, 61
grades of, 62high-purity mercury, 62non-volatile residues, 61
RCRA see Resource Conservationand Recovery Act (RCRA)
Resource Conservation and RecoveryAct (RCRA), 203, 205
Safe Drinking Water Act(SDWA), 203
Schroder’s equation, 38semiconducting compound synthesis
ampoule method, 168Bridgman method, 170–171cadmium and tellurium, 169cadmium–mercury
tellurides, 169chalcogenides, 163, 168
indirect synthesis seechalcogenides
cinnabar, reda-modification, 163
crystallization patterns, 167direct methods, 168, 169equiatomic compounds, 163Hg–Se system, 165HgTe, 165–166impurity content, 168integral Gibbs free energy, 171,
172monotectic reactions, 163–164phase diagrams, 163–165
photoconductive infrareddetectors, 166, 167
solubility product, 169standard enthalpy change, 166sublimation and resublimation
methods, 170thick-walled quartz
ampoules, 171vapor pressures, 168
Significant New Use Rule(SNUR), 204
small-scale gold miningartisanal gold mining
Au amalgam, 196Au–Hg binary phasediagram, 195
procedure, 194reasons for, 194river sands/crushed Au oremixing, 196
surface diffusion, 195environmental
degradation, 196–197mercury amalgamation, 193mercury pollution, 194remedies/improvements, 197
Superfund Amendments andReauthorization Act (SARA), 202
thermal expansion coefficient,20–21
Total Maximum Daily Load (TMDL)Regulations and Guidance, 205
Toxic Substances Control Act(TSCA), 203
UHP lamps see ultra-highperformance (UHP) lamps
ultra-high performance (UHP)lamps, 143, 153–154
vapor pressure measurement system(VPMS), 151
321Subject Index
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